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    Default Terms & Abbreviations

    This is a list of common automotive terms and their standard meanings, along with some slang & alternate meanings. It also includes most of the industry-standard abbreviations for engine management, emissions, and PIDs. Many are linked to photos & diagrams, but I've decided not to embed images directly in the list. If you notice errors or omissions, e-mail me your suggestions with a link to this thread.

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    1G: Ford 1st-Generation alternator, which uses an external fan, a V-belt pulley, & a remote 5-pin voltage regulator with grounded case to produce 35-90A, typically used on carburetor engines until the mid-80s. Reliable, but weak.
    2: combustion code for Otto 2-Stroke-Cycle Piston engines.
    2-cycle: (slang) See Two-Stroke Cycle.
    2-stroke: (slang) See Two-Stroke Cycle.
    2-stroke cycle: See Two-Stroke Cycle.
    2G: Ford 2nd-Generation alternator, which uses an external fan & external 3-pin voltage regulator to produce 60-100A, typically used on early fuel-injected engines from the mid-80s to the early 90s. Famous for catching fire, usually due to a poor connection at the rectifier.
    2V: 1) 2 Valves per cylinder; 2) 2 Venturi (barrel) (carburetor/vacuum).
    2WD: Two Wheel Drive. A powertrain system which delivers engine power to only one axle (either front or rear). AKA 4X2. Contrast RWD, AWD, FWD, 4WD.
    3-2 Timing Solenoid (3-2TS): A device that controls the timing valve.
    3G: Ford 3rd-Generation alternator, which uses an internal fan, multi-rib pulley, & external 3-pin voltage regulator (later versions only utilizing 2 of the pins) to produce 90-130A, used from the early 90s to the early 00s with much success. Noted for reliability & high output at all RPMs, and for being easy to retrofit into older vehicles.
    4G: Ford 4th-Generation alternator, which uses an internal fan & 3-pin voltage regulator (only utilizing 2 of the pins), and a multi-rib pulley to produce 90-130A, used from the early 00s to the late 00s.
    4R44E: 4 speed, Rear wheel drive, 440 lb-ft, Electronic transmission, derived from the C3/A4LD.
    4R55E: 4 speed, Rear wheel drive, 550 lb-ft, Electronic transmission, derived from the C3/A4LD.
    4R70W: 4 speed, Rear wheel drive, 700 lb-ft, Wide ratio electronic transmission, formerly known as AODE and AODE-W.
    4R100: 4 speed, Rear wheel drive, 1000 lb-ft, electronic transmission, formerly known as E4OD. After ~'99, 4R100s actually changed by gaining 2 integral speed sensors, but they're still backward-compatible with late E4ODs by abandoning the sensors in-place.
    4-cycle: (slang) See Four-Stroke Cycle.
    4-stroke: (slang) See Four-Stroke Cycle.
    4-stroke cycle: See Four-Stroke Cycle.
    4V: 1) 4 Valves per cylinder; 2) 4 Venturi (barrel) (carburetor/vacuum).
    4WD: Four Wheel Drive. A powertrain system which delivers engine power to differentials in both (front & rear) axles. AKA 4X4. Contrast RWD, AWD, FWD, 2WD.
    A/CL: Air Cleaner (carburetor/vacuum)
    A/CL DV: Air Cleaner Diverter Valve (carburetor/vacuum)
    A/CL BI MET: Air Cleaner BiMetallic valve (carburetor/vacuum)
    Accordion: See Crumple Zone.
    ACET: Air Conditioning Evaporator Temperature. AKA Evaporator Air Discharge Temperature
    ACON: Air Conditioning On.
    ACP: Air Conditioning Pressure.
    ACPSW: Air Conditioning Pressure Switch.
    ACT: Air Charge Temperature sensor. AKA IAT.
    Actuator: A mechanism for moving or controlling something indirectly instead of by hand.
    ACV: Air Control Valve (carburetor/vacuum)
    A/D: Analog-to-Digital signal conversion.
    Adaption: Adjustments to the operating strategy made by the PCM based on actual driving conditions & feedback. Adaptions are stored in KAM separate from DTCs & freeze frames. Clearing adaptions is a special function available only on certain scanners, but it also occurs if KAPWR or KAM fails. Without adaptions, the PCM operates on baseline PROM strategy until it relearns the adaptions, which typically requires varied driving over 10-20 miles.
    Advance: 1) the quality or quantity of ignition timing BTDC; 2) an auto parts store chain.
    AFCM: Alternative Fuel Control Module.
    A-Frame: A supporting structure used for lifting overhead loads. It may consist of a single "A"-shaped boom which pivots (as on inexpensive wreckers or on light-duty cranes), or 2 with a single beam between them to span a working area below.
    Aftermarket: 1. A general term for the industry that produces non-original parts for vehicles; see SEMA. 2. Non-original vehicle parts. Contrast Direct-Replacement.
    Ah: Amp hours: the amount of current a 12V battery can deliver over a given time period without falling below 10V . Common time periods range from 2-10 hours, and indicate the actual amount of energy stored within a battery. Higher Ahs over shorter periods are better, and those numbers come from larger, heavier batteries. Compare CA, CCA, HCA, RC.
    AIR BPV: Air ByPass Valve. AKA TAB (carburetor/vacuum)
    Air Conditioning (A/C): A vehicular accessory refrigeration system that modifies the passenger compartment air by cooling and drying the air using a belt-driven compressor with magnetic clutch, a condenser with fan, an orifice or expansion valve, an evaporator within an air handler, an accumulator/drier with dessicant, and various sensors & switches. As the refrigerant gas is compressed, its temperature rises, and it flows as a hot high-pressure gas into the condenser. The external airflow created by the fan cools the refrigerant (carrying heat away) so that it condenses to a warm high-pressure liquid. This liquid flows through the orifice tube or expansion valve, which creates a sudden pressure drop. The low-pressure liquid boils & becomes cold, collecting heat from the evaporator core, which in turn gets heat from the air within the passenger cabin. The cool low-pressure gas & liquid mix flows into the accumulator where any water is absorbed by the dessicant. The accumulator is designed to allow only gas to flow out & return to the compressor to repeat the cycle. If the cabin temperature is too low to boil the refrigerant, the low-side pressure falls below ~20psi, breaking the circuit to the compressor clutch. This prevents ice from forming on the evaporator AND prevents the system from ever dropping below atmospheric pressure, which could pull in contaminants. Early systems used R-12, but all systems now use R-134a.
    Air Conditioning Clutch (ACC): A sensor, signal, or circuit which indicates status of the A/C clutch.
    Air Conditioning Cycling Switch (ACCS): A sensor, signal, or circuit which indicates status of the A/C cycling switch.
    Air Conditioning Demand (ACD): A sensor, signal, or circuit which indicates status of the A/C demand switch.
    Air Conditioning On (ACON): A sensor, signal, or circuit which indicates status of the A/C system.
    Air Conditioning Pressure (ACP): A sensor, signal, or circuit which indicates pressure in the A/C system.
    Air Conditioning Pressure Switch (ACPSW): A switch used for additional A/C system pressure control. Also referred to as the refrigerant containment/fan function switch.
    AIR:Secondary Air[/URL] Injection.
    AIRB: Secondary Air Injection Bypass. AKA TAB
    AIRD: Secondary Air Injection Diverter. AKA TAD
    Air/Fuel Ratio: Air to fuel mixture ratio; 14.7:1 is also called stoichiometry. This value is monitored & stored by the PCM as the LAMBSE PID.
    Air-to-Air (A2A): a heat exchanger such as an intercooler for a forced-induction system.
    AKA: also known as.
    Al: Aluminum.
    Allen Key or Allen Wrench: A hardened driver whose functional end (if not the entire tool) is a male hex. Contrast Torx.
    Alternator[/URL]: A term trademarked by Chrysler Corporation. See Generator.
    ALVW: Adjusted Loaded Vehicle Weight, defined by (Curb Weight + GVWR)/2, or Curb Weight + (Payload/2).
    Ambient Temperature: Temperature of the air surrounding an object.
    AMG: 1) mega fuse; 2) a German customizing company for BMW & Mercedes; 3) American Motors General, the manufacturing consortium for many US military vehicles
    Amp: 1) Amplifier; 2) (slang) Ampere
    Ampere (A or i): the standard unit of measure for electrical current. It represents a specific number of electrons flowing past a given point per second, analogous to the flow rate of water.
    AN Fittings: Army/Navy fittings; a shape & sizing convention used on many military vehicles, and popular on modified civilian vehicles for its reliability & interchangeability. Sizes are preceded by a minus sign and represent the inside diameter in INCHES times 16 (-AN = inch x 16), so a -6AN fitting is 6/16" or 3/8" ID.
    Anaerobic: literally "without air": a chemical (usually an adhesive or sealant) that cures without being exposed to air, such as epoxy.
    Analog: 1. An electrical signal that can attain any value within the voltage limits of the signal, OR a mechanical display capable of any intermediate value. Contrast Digital 2. A substitue or simulation that functions similarly to the actual item.
    Analog Meter: A handheld tool with an analog (needle) display for measuring various characteristics of electrical/electronic circuits & components. Contrast DMM.
    Anti-lock Brake System (ABS): An electro-hydraulic system which prevents wheel lockup during an emergency stop by modulating brake pressure. Allows the driver to maintain steering control and stop the vehicle in the shortest possible distance under most conditions. Several versions exist including RABS, RABS-II, 3-channel 4WABS, 4-channel 4WABS, TA, & TC.
    A-Pillar: The front-most body structure for supporting the roof of a vehicle. Subsequent pillars are designated "B", "C", etc.
    AOD[/URL]: Automatic Overdrive transmission, derived from the FMX. It evolved into the AODE, 4R70W[/URL], 4R44E, 4R55E, 5R55W.
    AODE[/URL]: Automatic Overdrive Electronic transmission, derived from the AOD (FMX). It evolved into the 4R70W, 4R44E, 4R55E, 5R55W. AKA AODE-W.
    APM: mini blade fuse. AKA ATM.
    APR: standard or regular blade fuse. AKA ATC, ATO.
    APS: micro or mini low-profile blade fuse. AKA ATM.
    APX: maxi blade fuse.
    ARB: An aftermarket manufacturer of bumpers & a pneumatic selectable-locking differential. Compare E-Locker.
    ARC: Automatic Ride Control.
    Articulation: Movement of the suspension, especially to its extremes (front & rear suspensions in opposite directions) when off-roading.
    ASCII: American Standard Code for Information Interchange; a standardized digital binary code of letters, numbers, & symbols used in most computers.
    ASE[/URL]: Automotive Service Excellence; an organization that establishes & maintains standards in the auto service industry, most notably by adminstering tests for technicians & other auto service personnel.
    A/T: Automatic Transmission/Transaxle.
    ATC: standard or regular blade fuse. AKA APR, ATO.
    ATDC: After Top Dead Center; a time or angle of a given crankshaft lobe (usually #1) just after it has aligned with its connecting rod, and the piston is moving toward the crankshaft.
    ATF: Automatic Transmission Fluid; any of several non-compatible types of hydraulic oil, used in automatic transmissions[/URL], power steering systems[/URL], hydraulic brake boosters, manual transmissions[/URL], & transfer cases. Examples include: Type A, Type F, Mercon (I-V), MerconSP, MerconLV, FNR5, CVT, Dexron (I-V), ATF+2, ATF+3, ATF+4.
    ATM: mini, micro, or mini low-profile blade fuse. AKA APM, APS.
    ATO: standard or regular blade fuse. AKA ATC, APR.
    Automatic Ride Control (ARC): A system that automatically adjusts the suspension system to accommodate varying road and driving conditions.
    Averaging Bank/Trade: Used for Nox Credits on Heavy Duty Trucks Only.
    AWD: All Wheel Drive. A powertrain system which delivers engine power through a differential in the transfer case to differentials in each axle. Some newer cheap AWD systems use a viscous coupling between the front & rear axles instead of a differential. Contrast RWD, FWD, 4WD, 2WD.
    AWG: American Wire Gauge; a number representing the effective cross-sectional area of an electrical conductor. The standard scale ranges from 0000 (0.460", ~12 mm) to 36 (0.005", ~0.13 mm) in 39 steps, with each higher gauge having 0.890526 the area of the preceding gauge. Stranded wire has a larger actual cross-section than solid wire of the same gauge due to the air spaces between the strands.
    AX4N: Automatic 4 speed Non-synchronous transaxle (front-wheel drive).
    AX4S: Automatic 4-speed Synchronous transaxle (front-wheel drive).
    Axle: A structure which bears the weight of a chassis onto wheels, through bearings & hubs. Driven axles also contain mechanisms to transmit torque to the hubs. Steering axles further contain mechanisms to allow the wheels to swivel. Axles may be solid (monobeam) or independent. Each hub may be attached to 1 or 2 wheels.
    Axle Wrap: A condition that affects leaf spring solid axle suspensions in which the spring pack isn't strong enough to withstand the torque under hard acceleration, and it flexes into an "S", slightly wrapping around the axle tube. Eventually, the tire breaks free, the torque is released violently, and the driveline suffers (usually catastrophic) impacts as the tires bounce and catch. There are several ways to reduce or eliminate the condition, including stronger springs, traction bars, or a multi-link suspension.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    B+: Battery Positive Voltage.
    Back-tap: A special tap used for chasing damaged threads. Its cutting edges compress so the tool can be inserted past the damage, and then expanded to engage the good threads before working backward out of the hole.
    Backfire: Combustion that occurs in the intake, causing flame & noise to emanate from the throttle. It can be caused by incorrect valve or ignition timing, a lean mixture, or fuel leaks. It can damage the carburetor, the throttle plates, sensors, the intake ductwork, anything under the hood, the hood, or even start a fire.
    Backout: a failure of a terminal to remain mechanically in-place within its connector shell. The terminal is pushed back within the shell, preventing it from making good contact with the mating terminal, resulting in an open circuit, or intermittent open circuit, or high resistance.
    Backprobe: To connect a meter to a circuit by inserting a probe into the back of an electrical connector where the metal terminals may be accessed without separating the connector, or piercing the wire's insulation.
    Ball Joint (BJ): A spherical joint used mainly to connect a steering knuckle to a suspension arm; it has largely replaced the kingpin since it eases design & manufacture, and it allows fine & coarse adjustments for wheel alignment.
    BARO: Barometric Pressure.
    Barometric Pressure (BARO): A sensor, signal, or circuit which indicates the pressure of the surrounding air at any given temperature and altitude. See MAP.
    Barrel Roll: A side roll all the way back onto the wheels at least once.
    Base Idle: Idle rpm determined by the throttle lever hardset on the throttle body with the IAC solenoid disconnected. It is preset at the factory & should never be adjusted.
    Base Timing: Spark advance in degrees before top dead center of the base engine without any control from the PCM or ICM (EFI), or any vacuum- or centrifugal advance (carb).
    Battery: An electrical storage device designed to produce a DC voltage by means of an electrochemical reaction. Common automotive batteries develop ~13.2VDC using six 2.2V lead & sulfuric acid cells, with the negative (-) terminal grounded to the chassis, body, & engine.
    Battery Positive Voltage (B+): The voltage from the battery positive post or any circuit connected directly to the battery, relative to the battery negative post, or chassis ground. Compare VPWR, VREF.
    Battery Saver: a circuit for key-off accessories controlled by a module to disable the circuit after a preset time (usually 15 minutes). Compare Retained Accessory Power.
    BATTEMP: Battery Temperature.
    BBL: Barrel (carburetor/vacuum). Compare Venturi.
    BCI: Battery Council International, a non-profit trade organization that establishes standards for autmotive batteries; particularly, physical sizes.
    BCM: Body Control Module - an electronic component that generally controls systems unrelated to the powertrain. AKA GEM, BSM, CSM...
    Bench-Testing: 1) testing a part or system on a fixture that simulates normal use; 2) (slang) guessing about the way something will work.
    Bendix: 1) A manufacturer of OE & direct-replacement auto parts; 2) (slang) A one-way starter drive gear.
    Bevel Gears: A common gear design resulting in an angled drive. The radial gear teeth are on an angled surface (like a truncated cone), and their axes intersect where the tips of the cones would be, typically in a right angle. Contrast Helical, Herringbone, Hypoid, Spur, Worm.
    BFH: (slang) Big F*****g Hammer.
    BI: fuel code for Other Bi-Fuel
    Bigblock: An engine family of varying displacements that share some parts & characteristics, most of which have higher displacement than most of those in another family of engines from the same manufacturer within the same model year range. Contrast Smallblock, Short Block, Long Block.
    Billet: A dense form of metal (usually Aluminum) made by mechanically compressing a cast ingot to eliminate any internal pores, and then re-heating (annealing) it to relieve internal stress & re-crystallize it.
    Binary: a simple numbering system using only two possible characters (usually 0 & 1) in each digit. "Bi-" means two. The binary representation of one is "1" or "00000001" (any amount of preceding 0s); two is "10"; three is "11"; nine is "1001"; fourteen is "1110". 8-bit binary contains 8 digits per value (byte, word); 16-bit contains 16 characters per value, so two in 16-bit binary is "0000000000000010".
    Bit: a digital position within a numeral, capable of containing any valid character used in that numbering system.
    BJB: Battery Junction Box.
    Bk: Black wire or vacuum line.
    BL: Body Lift.
    Blade Fuse: A plastic-encased flat fuse with parallel flat terminals that replaced the glass tube fuse in the early 80s. Sizes are: APS/ATM Low Profile/Micro, APM/ATM Mini, APR/ATC/ATO Blade, and APX/Maxi, ranging from 0.5A to 150A.
    Blinker Fluid: A joke among mechanics & gearheads to detect amateurs.
    Block Test: See Dissolved Gas Test.
    Blower[/URL] (BLR): 1) A device designed to supply a current of air at a moderate pressure, typically through a ventilation system. It usually consists of an impeller assembly, a motor and a suitable case. The blower case may also function as part of the ventilation system and contain diverter doors and other apparatus; 2) a supercharger.
    BLR: Blower.
    Blue Point: An imported brand of tools marketed by Snap-On.
    Blue Wrench: (slang) a torch, because of its blue flame. AKA Red Wrench because it makes things red-hot.
    Bn: Brown wire or vacuum line.
    Body Lift (BL): The modification of a vehicle's ride height by spacing the body up from the frame, usually to allow for larger tires. It does not increase ground clearance, suspension travel, or approach/breakover/departure angles. It increases body sway, and the danger of the body shifting on the frame during a collision. Steering & shifting linkages usually must be adjusted, and hoses lengthened. See Lift. Contrast Tire Lift, Suspension Lift.
    Body Mount: a rubber isolator (sometimes with steel sleeves) between the frame & cab. AKA Cab Mount.
    Bolt: A medium- or heavy-duty machine-threaded fastener[/URL], generally with a hex head to be driven by a wrench into either a threaded hole or a nut. See Grade. Contrast Screw.
    Boom: A low resonant sound, like a drum roll or distant thunder.
    Booster Cables: A pair of light or medium wires with a connector or clamps capable of supplying under 120A from one vehicle to another for the purpose of recharging a weak battery over several minutes before attempting to crank the engine. Contrast Jumper Cables.
    Booster Pack: See Jumper Battery.
    Bore: the inside diameter of an engine cylinder. See also: Stroke.
    Bored (Overbored): Modified by increasing the bore.
    Box Van: A modified or aftermarket vehicle body using the cab & hood of a van or light truck, with a simple enclosed cargo box conjoined, like most ambulances. If the cargo area is not accessible from the passenger cabin, it's not a box van - just a cargo truck with a box.
    Boxed or Boxed Frame: A frame constructed of hollow tubular members, as opposed to open channel members. It may be designed that way, or the result of adding material to a channel frame to enclose the members. Early Broncos & most Land Rovers have fully-boxed frames from the factory. '80-96 F-series & Broncos are only factory-boxed between the front bumper and the back of the first crossmember.
    BPA: Bypass Air; see IAC.
    BPA-ISC: Bypass Air Idle Speed Control solenoid; see IAC.
    BPH: Ball-Peen Hammer; a steel hammer with one flat face & one hemispherical face for peening rivets, and other metalwork.
    BPP: Brake Pedal Position.
    Br: Brown wire or vacuum line.
    Brake or Brakes: 1) a system for slowing a moving vehicle, or holding it stationary; 2) the pedal, lever, or other mechanical components to control such a system; 3) the friction components of such a system.
    Brake On/Off[/URL] (BOO): A binary switch which indicates the position of the brake pedal &/or activates the brake lights. It may also perform other functions. Compare BPP, Stop Lamp Switch[/URL].
    ]Brake Pedal Position[/URL] (BPP): A multi-contact or analog sensor, signal, or circuit which indicates the position of the brake pedal for use by the traction control &/or restraint systems. Compare BOO.
    Break: 1) to fail, fracture, or shatter; 2) to free, loosen, or unseize.
    Breakout Box: A service tool that "tees" between the PCM and the matching harness connector. The breakout box contains test pins that can be probed for EEC system testing without the risk of damage to the EEC, its wiring, or its connector by direct probing.
    Brinelling: the process by which bearings damage their own races due to LACK of movement under high loading. The race develops an imprint of the loaded bearing, resulting in looseness, noise, and accelerated wear.
    BSM: Body Security Module, AKA BCM, CSM, GEM...
    BTDC: Before Top Dead Center; a time or angle of a given crankshaft lobe (usually #1) just before it has aligned with its connecting rod, and the piston is approaching its maximum distance from the crankshaft. Ignition spark usually occurs during this phase.
    Bus+ or -: Bus positive or negative.
    Bu: Blue wire or vacuum line.
    Bus positive or negative (Bus+ or -): Circuits that carry data to & from the various modules on a network, & the DLC.
    Buzz: A steady low-pitched noise, typically accompanied by a vibration.
    BV: Bowl Vent (carburetor/vacuum)
    BW 1345: A rare chain-driven 4WD (no internal differential) part-time 2-speed transfer case built by Borg-Warner with a fixed front yoke output on the L side. It replaced the NP 208F for a few years in heavy-duty light trucks until it was replaced by the 1356, and was always built with a fixed rear output yoke.
    BW 1356: A common chain-driven 4WD (no internal differential) part-time 2-speed transfer case built by Borg-Warner with a fixed front yoke output on the L side & a magnesium-alloy case. It replaced the NP 208F & BW 1342, and was built in several configurations: manual-shift/ESOF; with PTO (Aluminum front case)/without; with/without speedo gear bore; fixed/slip rear output; yoke/companion flange fixed rear output. It was used in 1/2-ton pickups & Broncos, and F350s w/PSTD, so it's a VERY strong box.
    Byte: a group of bits (usually 8 or 16, though modern PCs are 32- or 64-bit) interpreted & processed as a single value. A numeric "word".

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    C: 1) Chemical symbol for Carbon; 2) fuel code for CNG.
    Cab or Cabin: The passenger compartment of any vehicle or equipment; cab usually refers to trucks & equipment to distinguish from the detached cargo bed or working appendages; cabin usually to cars & SUVs to distinguish from the integral engine bay &/or cargo trunk, but not from an integral interior or convertible cargo bed (wagon bodies).
    CAC: Charge Air Cooler. Formerly known as Intercooler. A device which lowers the temperature of pressurized intake air.
    CAFE: Corporate Average Fuel Economy. A set of federal requirements and regulations which govern fuel economy standards for all motor vehicles produced by one corporate entity.
    California Air Resources Board (CARB): a governing body of California which establishes air pollution laws.
    Camshaft: A shaft on which phased cams are cut or mounted. The cams regulate the opening and closing of the intake and exhaust valves in the head(s). See also OHC, OHV, VVT.
    Camshaft Position (CMP): A sensor or signal which indicates camshaft position.
    Canister (Carbon or Charcoal): An evaporative emissions system component which contains activated charcoal which absorbs fuel vapors and holds them until the vapors can be purged into the intake to be burned in the engine.
    Canister Purge (CANP): A circuit or solenoid valve which controls airflow through the carbon canister into the intake manifold.
    Canister Vent (CV or CANVNT): A circuit or solenoid valve which controls airflow between the carbon canister and the atmosphere.
    Carb: (slang) Carburetor
    Cardan Joint: A type of universal joint consisting of 2 shafts at right angles connecting 2 yokes. AKA Hooks Joint
    Cardone: An aftermarket parts remanufacturer (A1 Cardone).
    Carter pin: (slang) mispronunciation of Cotter Pin.
    Cascade Failure: a progressive (and usually catastrophic) failure sequence, beginning with a single (usually minor) failure that triggers several more, each which may trigger several more, and so on.
    Case Ground (CSE GND): PCM case ground circuit or terminal.
    Catalytic Convertor: An in-line exhaust system device used to reduce the level of engine exhaust emissions by the use of catalysts (chemicals which cause chemical reactions without being consumed in those reactions). Most catalysts are deactivated by Lead, which is why unleaded fuel was introduced. Some cause HC to be oxidized; some cause NOx to be reduced; some convert other pollutants into non-toxic compounds.
    CB: 1) Citizens' Band; 2) classic Bronco (usually '66-77)
    CC: 1) cubic centimeter; 2) the process of measuring the precise volume of a cylinder head by draining water from a graduated cylinder into the combustion chamber, so called because most graduated cylinders are graduated in ccs.
    CCM: Comprehensive Component Monitor.
    CD: 1) Compact Disc - any of several types of 5 inch optical medium for audio in the CDA format, or video in the VCD, SVCD, DVD, DVD-DL, HDDVD, or BD formats, or for data in any digital format; 2) Coil Driver.
    Centralized Testing Facility: A state government inspection/maintenance (IM) and safety station.
    CD4E: CD class vehicle, 4 speed, Electronic transmission.
    Chain(s): 1) A steel recovery chain; 2) tire chains; 3) a timing or transfer case chain.
    Chase (Threads): to repair machine threads by reforming or recutting with a tap, die, file, or rethreading tools; to clean machine threads by running mating threads over them while rinsing with oil.
    Chassis: The working components of a vehicle, not including the body or its wiring.
    Chassis grease: Any of a wide range of greases (usually Lithium-based) for general use on vehicles.
    Check Engine Light (CEL): A warning light used to indicate a fault has been detected either in the engine, transmission, or emissions systems. Some can be triggered to flash out fault codes. AKA MIL.
    Circuit: 1) A complete electrical path or channel from the negative side of a voltage source through a load and back to the positive side, usually including that voltage source; 2) the electrical conductor pathway (wire or ground); 3) an analogous conduit for fluids, as in hydraulic or pneumatic controls.
    Citizens Band (CB): 1) A band of low radio frequencies deregulated by the FCC for civilian use; 2) A radio which operates in that band.
    Clean Tach Output (CTO): A signal or circuit used to drive the instrument panel tachometer.
    Closed Loop (CL): An operating mode which manages outputs based on sensor feedback. Contrast Open Loop.
    Clutch: A mechanism for connecting & disconnecting 2 rotating assemblies or shafts, such as an engine & transmission, or a pulley & compressor.
    CMVSS: Canadian Motor Vehicle Safety Standards.
    CNG: Compressed Natural Gas. See Natural Gas. Compare LNG; contrast LPG.
    CO: Carbon Monoxide; a colorless, odorless, tasteless, poisonous gas produced by incomplete combustion. It is heavier than air, and settles into low areas. It works in red-blooded animals by permanently attaching to the hemoglobin, preventing fresh Oxygen or waste CO2 from attaching. The result of over-exposure is nausea, drowsiness, bright red skin, and death. It is not removed from the body until the affected blood cell dies, or is transfused out.
    CO2: Carbon Dioxide; a colorless, odorless, poisonous gas produced by respiration & combustion. It is slightly heavier than air, but disperses rapidly. Overexposure results in confusion, exhaustion, skin lesions & burns, choking, watering eyes, and death.
    Coast Clutch Solenoid (CCS): Controls the application and release of the coast clutch in the transmission.
    Coil: 1) A device consisting of conductors wrapped around a magnetizable core, often used to increase the voltage in a spark ignition system; 2) a coil spring.
    Cold-Rolled or Cold-Formed: A metal part which has been reshaped (OTHER than by cutting or hammering) below its eutectic temperature, resulting in internal stresses & work-hardening. Contrast Hot-Rolled, Hot-Formed, Annealed.
    Cold Soak: Time given to a vehicle to sit at a low temperature (typically below 68° F / 20° C) until the temperature of external and internal components stabilize.
    Combo: a small module attached to '87-91 truck instrument clusters which triggers an EMISSIONS warning light. It serves no purpose since no supplier (including Ford) ever made the parts it was intended to indicate were due for replacement.
    Compression Test: a basic procedure for checking the general condition of an engine by measuring each cylinder's ability to create pressure, and then comparing those numbers to each other (NOT to any fixed standard). Most engines are considered passing if the lowest cylinder is >75% of the highest, and adjacent cylinders are within 20%. Initially, the test is performed with the cyinders empty (dry); if there's a failing cylinder, it is retested with engine oil added (wet). Compare Leakdown Test.
    Compression Ratio (CR): the ratio of the volume of the compression chamber to that PLUS the piston's displacement. Most engines are built for approximately 8:1; high-performance engines are around 9:1; diesels are above 11:1. Deposits in the combustion chamber or on the pistons will raise the CR, sometimes to levels that will damage the engine. Compare cc.
    Compressor: A pump that takes in relatively low-pressure gas and releases very high-pressure gas at low flow rates, usually to be condensed into a liquid after passing through an heat exchanger (intercooler or condenser).
    Computer Controlled Dwell (CCD): A variant of the TFI-IV ignition system in which the EEC processes several signals into the SPOUT, and the ICM uses both the rising & falling edges of that signal to control both ignition timing AND dwell. Contrast Push-Start.
    Computed Timing: The total spark advance in degrees before top dead center; equal to base timing plus/minus an additional factor calculated by the PCM based on input from a number of sensors.
    Constant Control Relay Module (CCRM): A relay module that provides on-off control of various EEC components.
    Continuous Duty: In operation without interruption. Some devices (usually electrical relays, solenoids, & motors) are designed only for intermittent use; others can tolerate constant on-time, without overheating or wearing out prematurely.
    Continuous Memory (CM or CONT): The portion of KAM used to store DTCs generated during the Continuous Memory Self-Test.
    Continuous Memory Self-Test: A continuous test of the EEC system conducted by the PCM whenever it is operating.
    Control: A means or device which directs and regulates a process, machine, apparatus, or system.
    Coolant: A fluid used for heat transfer; typically water. Coolants usually contain additives such as rust inhibitors and antifreeze/antiboil agents like ethylene glycol. They may also contain bittering agents to discourage consumption since most additives are toxic and sweet.
    Cotter Pin: a shear pin made of wire folded onto itself so the open ends can be separated to retain the pin in its bore, and straightened for removal.
    CPP: Clutch Pedal Position sensor, switch, or circuit.
    CQIS: Common Quality Indicator System.
    Crankshaft: The part of an engine which converts the reciprocating motion of the pistons to rotary motion, and connects to the transmission. It also usually drives the engine accessories.
    Crankshaft Position (CKP): A sensor, signal, or circuit which indicates crankshaft position.
    Cryogenic: Any process involving temperatures significantly below 0F; often involving liquid Nitrogen or dry ice.
    Civilian Utility Cargo Vehicle (CUCV): a military version of the GMC/Chevy Blazer (fullsize 4WD) or Ford Bronco
    Civilian Utility Truck Vehicle (CUTV): a military version of the GMC/Chevy K3500 pickup truck (4WD)
    Curb Idle: The idle rpm when the engine is at normal steady-state operating conditions.
    Cylinder Head Temperature (CHT): A sensor, signal, or circuit which indicates the temperature of the engine cylinder head.
    Cylinder Identification (CID): A sensor, signal, or circuit which provides crankshaft or camshaft position information for fuel injection synchronization.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    D: 1) Drain (ammeter or Alt gauge) indicates the alternator is supplying LESS current than the vehicle is consuming, so the battery is discharging; 2) combustion code for Diesel Cycle; 3) fuel code for Diesel
    Daily Driver (DD): A vehicle comfortable & reliable enough to be used every day for commuting, but which isn't necessarily suited to work (hauling/towing) or play (off-roading). Compare Grocery-Getter, Weekend Warrior.
    Dashpot: A vacuum diaphragm that controls the throttle stop &/or closing speed to assist with idle control and reduce run-on (carburetor/vacuum)
    Data: General term for information, usually that has been simplified into numbers, letters, or symbols.
    Data Link Connector (DLC): J1962 or EEC-IV connector providing access and/or control of the vehicle information, operating conditions, and diagnostic information.
    Data Output Line (DOL): A circuit that sends certain information from the PCM to the instrument cluster.
    Data Positive or Negative (DATA+ or DATA-): Circuits that carry data to the DLC, Message Center, or VCRM.
    DATA+ or DATA-: Data Positive or Negative.
    Daytime Running Lamps (DRL): A system that keeps the vehicle headlamps on at all times (though often at reduced power & without marker lamps) while the vehicle is operating.
    Db: Decibel, a logarithmic measurment of sound intensity.
    DB: Dark Blue wire or vacuum line.
    DC: 1) Direct Current. Electric current flowing in one direction, as from a battery; 2) Duty Cycle. The ratio of ON time versus the sum of ON & OFF times, expressed in percent.
    DCL: Data Communication Link. See Data Link Connector.
    DD: 1) Direct Drive; 2) Drunk Driving; 3) Daily Driver.
    DDM: Driver's Door Module - an electronic component that controls systems related to the driver's door, including PL, PW, OTD, KE, RKE.
    Decimal: a common numbering system using ten possible characters in each digit, based on human fingers. "Deci-" means ten.
    DEF: 1) Defroster; 2) Diesel Emissions Fluid: 32.5% urea + 67.5% deionized water injected into diesel exhaust to reduce NOx emissions.
    Defroster (DEF): 1) A function of the HVAC system's coolant heat exchanger (heater core) to remove frost from the front windows of a vehicle; 2) An electrically heated device designed to remove ice, frost, or snow from the rear window of the vehicle; 3) Electrical wires embedded in vehicle windows to remove frost.
    Detonation: See Knock.
    Detroit Locker: An aftermarket locking differential famous for reliability & robustness, now manufactured by Eaton.
    DFR: Dual-Function Reservoir
    DG: Dark Green wire or vacuum line.
    DI: 1) Distributor Ignition, see TFI-IV; 2) Direct Injection.
    Diagnostic Test Mode (DTM): A level of capability in an On-Board Diagnostic (OBD) system. This may include different functional states to observe signals, a base level to read Diagnostic Trouble Codes, a monitor level which includes information on signal levels, bi-directional control with on/off board aids, and the ability to interface with remote diagnosis.
    Diagnostic Trouble Code (DTC): An alpha/numeric identifier for a fault condition identified by the On-Board Diagnostic System.
    Diags: 1) Diagonal wire cutting pliers, often misspelled "dykes" or "dikes"; 2) Diagnostics.
    Dial Indicator: A calibrated instrument for measuring very small linear movement; usually less than 1" by thousandths. They are often used to measure cam lobes, concentricity of crankshaft journals, bends in rotating shafts, endplay in shafts, backlash in gears, runout in brakes, and slop in spherical joints. They can be mounted by fastener, magnet, clamp, or other means.
    Die: A tool for cutting external threads onto a shaft or rod. Contrast Tap, Thread Chaser, Thread File.
    Dielectric: Electrically insulating.
    Dielectric Grease: A thick type of silicone grease designed to prevent electrical connection, while still allowing heat transfer between bare metal parts, like transistors & heat sinks. It is also useful as a high-temperature lubricant. It is often MISused on electrical terminals to block Oxygen & moisture in order to improve the durability of the connection. On larger terminals (like battery posts), the larger surface area can allow the grease's high film strenght to break or severely inhibit the electrical connection. Compare Thermal Grease. Contrast Electrical Grease, Chassis Grease.
    Diesel: 1. A german scientist who invented a simple & reliable engine which can run efficiently on very low-grade fuel oil; 2. An engine which operates on the Diesel (2-stroke or 4-stroke) cycle; 3. The fuel for such engines. Untaxed diesel fuel (for agricultural use) in the US has a dye added so that inspectors can tell if it was used in taxable vehicles.
    Dieseling: See Knock.
    Differential (Diff): A mechanism for dividing the engine's power between 2 shafts, most often between the 2 axleshafts within an axle or transaxle, but also sometimes between 2 driveshafts within an AWD transfer case. Most are "open", meaning the mechanism is allowed to work without limitation, which results in the input torque being split inversely to the output resistance (the tire with the least traction gets the most torque). Others may contain clutches (limited slip) or more complex mechanisms (torque-biasing) to restrict the division of torque and aid in traction. Contrast Spool, Lincoln-Locker, 4WD.
    Differential Pressure: The pressure difference between two regions, such as between the intake manifold and the atmospheric pressures.
    Differential Pressure Feedback EGR (DPFE): An EGR system or its primary sensor that monitors EGR pressure across a remote orifice to control EGR flow. AKA Dual Pressure Feedback EGR
    Digital: 1) An electrical signal that is stepped among certain possible values within the voltage limits of the signal; 2) a display capable of only certain preset values/elements occurring only in certain positions; 3) controls which process information by switching the current or voltage through steps. Contrast Analog, Binary, Decimal, Hexadecimal.
    Digital MultiMeter (DMM): A handheld tool with a digital display for measuring various characteristics of electrical/electronic circuits & components. Digital meters require less current from the circuit being tested and produce more accurate & precise readings. They also generally have more features and cost far less than older meters. Contrast Analog Meter.
    Digital Transmission Range sensor (DTR or TR[/URL]): A sensor, signal, or circuit which indicates the selected modes of the transmission. It may be used for PCM control of shifting, cruise &/or starter interrupt. AKA MLP, MLPS, PNP, NSS.
    Digital Volt-Ohm Meter (DVOM): A handheld tool with a digital display for measuring voltage or resistance characteristics of electrical/electronic circuits & components. See DMM.
    Dikes: See Diags.
    Diode: an electronic component that allows current to flow only in 1 direction along a circuit, and also creates a voltage drop (typically ~0.7VDC). When polarity is reversed, the voltage drop goes above 100VDC until it reaches the semiconductor's breakdown voltage. They are commonly used to drain inductance spikes across solenoid or relay coils; to convert AC into rough DC (inside alternators & transformers); to prevent semi-independent circuits from interfering with each other (like a dome light & cargo light); and to create constant smooth voltage for delicate circuits (like Zener diodes in a power supply). Some emit light (LED) and are becoming more popular as high-efficiency long-life light sources. See Light-Emitting Diode.
    Direct Injection (DI): A cylinder head design in which the fuel injector pintle is within the combustion chamber.
    Direct-Replacement: Parts engineered to be equivalent (in fit & performance, if not appearance) to OE parts, but produced by non-OEM.
    Disk Brakes: A braking system based on a 2-sided brake rotor with a pad wearing against each side. The pads are compressed against the rotor by a caliper (usually hydraulic), creating a braking force on the rotating hub. They are less complex than drum brakes, and are less affected by extended use, fording, or high speed. See also Cross-drilled Rotor, Slotted Rotor, Drum-in-Hat. Contrast Drum Brakes.
    Dissolved Gas Test: A quick test to detect block & head cracks by checking for exhaust gases in the coolant system. A squeeze bulb is used to draw air from the coolant system through a special chemical which changes color (usually blue to yellow) if exhaust is present. AKA Block Test.
    Distributor: A mechanical device designed to switch a high voltage secondary circuit from an ignition coil to spark plugs in the proper firing sequence.
    Distributor Ignition (DI): A system in which the ignition coil secondary circuit is switched by a rotating mechanism in proper sequence to various spark plugs.
    DM: fuel code for Bi-Fuel, Diesel/Methanol
    DMM: Digital MultiMeter. Compare DVOM. Contrast Analog Meter.
    DOHC: Dual Overhead Cam.
    DOL: Data Output Line.
    Door Jamb Sticker: See Safety Certification Label.
    DOT: Department of Transportation. A federal office which oversees (among MANY other things) roads & motor vehicles.
    Double Cardan joint[/URL]: an assembly of 2 cross-type U-joints linked by a very short coupling with a mechanism between them to hold the coupling at exactly 1/2 the total flex angle across the assembly. It provides near-constant angular velocity through the joint, and allows nearly double the flex angle of a single cardan joint.
    Double Clutch: Releasing the clutch pedal suddenly to launch the vehicle, then pressing it to let the engine rev up again, and releasing a second time. With the correct engine/vehicle combination, it can reduce takeoff time by using the engine's momentum in addition to its power to get the vehicle moving. Contrast Speed Shift.
    Double Hex: A style of fastener & matching tool with 12 120° points. Contrast Triple Square.
    DPFE or DPFEGR: Differential (Dual) Pressure Feedback EGR. Compare PFE, EEGR, EVP.
    Drag Link: A steering link that directly joins the steering knuckles.
    DRI: Deposit Resistant Injector. A fuel injector designed to prevent buildup of carbon and other unwanted deposits used since the mid-80s.
    Drift: 1) A solid shaft tool used with a hammer to drive other objects, such as pins, often confused with "Punch"; 2) A driving technique involving sliding the rear wheels continuously sideways on pavement through an extended turn, purely for its dramatic effect. Contrast Fish-Tail.
    Drilled Rotor: See Cross-drilled Rotor.
    Driveability: A classification of vehicle concerns, including engine performance, transmission behavior, and drivetrain harshness.
    Drive Cycle: A long process during which a vehicle is operated in most normal driving states, but in a specific order for a specific time each, and with certain states repeated. Normal driving will eventually produce a drive cycle, but it can take months, depending on the driver, the weather, the traffic, and the roads. Certain emissions monitors require a drive cycle before they can reset after codes are cleared.
    Driveline: 1) See Drivetrain, 2) See Driveshaft.
    Driveshaft (D'shaft): A shaft connecting a transmission or transfer case to an axle or differential. It is usually tubular, either steel, Aluminum, Aluminum-Metal Matrix (AMMX), or composite. It usually includes at least 1 U-joint, CV joint, or rubber coupling disk at each end, & a slip joint (to allow for compression & extension). For longer distances, an intermediate joint & carrier bearing may be used.
    Drivetrain: The collection of parts within a vehicle that cause it to move, including the engine, transmission, driveshaft, & drive axle. AKA Driveline, Powertrain.
    DRL: Daytime Running Lamps.
    Drum Brakes: A braking system based on a wide cast-iron hoop with a thin plate on one side surrounding 1 or 2 shoes covered in friction material, which are themselves attached to a large plate on the suspension (usually a solid axle), enclosing the entire mechanism. The shoes are spread against the hoop's inner surface either by a hydraulic slave (wheel) cylinder, or by a scissor mechanism, or by a lever mechanism, and usually also by an adjusting mechanism (usually automatic). See also Drum-in-Hat. Contrast Disk Brakes
    Drum-in-Hat: A brake system combining a small drum brake (usually only for emergency/parking use) inside the rotor of a disk brake (usually on the rear axle). See Disk Brakes, Drum Brakes.
    DTC:Diagnostic Trouble Code
    DTM: Diagnostic Test Mode.
    DTR: Digital Transmission Range sensor.
    Dual Exhaust: an system that provides 2 equal-sized paths for the engine exhaust from the manifolds (or headers) to the tailpipes. "True" dual exhaust has no connection between the 2 pipes, which is less efficient than a well-engineered crossover.
    Dual-Function Reservoir (DFR): A pressure-operated fuel tank switching valve with an integral reservoir which may contain a filter. It is only used on dual-tank Ford trucks from '84-89 and is notoriously unreliable.
    Dual Overhead Cam (DOHC): An engine configuration that uses two camshafts in each cylinder head, positioned above the valves.
    Duckbill: The common term for a specific style of plastic quick-connector used on some fuel line & heater hose fittings. Compare Garter Spring, hairpin.
    D.U.I.: 1) Davis Unified Ignition - an ignition system common on '80-00 GM vehicles, and a popular modification on many others. It involves a distributor with integrated pickup, advance, coil, & module requiring as few as 1 wire to work. 2) Driving Under the Influence of drugs or alcohol, a.k.a. DWI, DD.
    Dust Cap: The outboard cover for a hub. Some include the knob or dial for manual hub locks on 4WD vehicles.
    DVOM: Digital Volt-Ohm Meter. Compare DMM.
    DWI: Driving While Intoxicated.
    Dye: A chemical additive used for visual identification or diagnosis, often fluorescent (UV).
    Dykes: See Diags.
    Dynamic: Moving/changing. Contrast Static.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    E4OD: Electronic 4-speed Overdrive automatic transmission introduced in '89 based on the C6. One of the strongest, longest, & heaviest automatic transmissions ever put in a light truck. Models built before 1995 developed a poor reputation. Renamed 4R100 ~'97. One of the running changes ~'99 was a PWM TCC solenoid to replace the earlier On-Off solenoid, and the corresponding orifice in the pump body changed from 0.030" to 0.250". This makes early & late E4ODs & their EECs/PCMs non-compatible without internal transmission mods.
    E: 1) combustion code for Electric; 2) fuel code for Ethanol; 3) EGR vacuum supply port (carburetor/vacuum)
    E85: Fuel containing 85% ethanol (ethyl alcohol). Pure ethanol is the alcohol which is the intoxicating agent in liquor, beer and wine. It is distilled from the fermentation of plants such as field corn and sugar cane. A denaturant that imparts a bad taste is added to ethanol to preclude consumption. Up to 5% hydrocarbons (such as unleaded gasoline) is a typical denaturant. The resulting denatured ethanol is designated Ed100 when used as a feedstock for motor fuels. Fuel ethanol (Ed85) is then made by adding 15% more unleaded gasoline. The resulting fuel also has a higher octane rating than unleaded regular gasoline, allowing engine designs with higher compression and corresponding greater engine efficiency and performance (power). Winter blends may contain up to 25% unleaded gasoline (plus the denaturant) to enhance cold engine starts, hence the sometimes used Ed85-Ed75 designation. Severely cold weather may require additional measures for reliable starting. Ethanol is more chemically active than gasoline. It corrodes some metals and may cause some plastic and rubber components to swell, break down, or become brittle and crack, especially when mixed with gasoline. Special materials and procedures are used with Ethanol FFVs. Ethanol has less energy per gallon than gasoline, so fuel economy in miles per gallon will decrease as the percentage of ethanol goes up. However, the decrease is not as severe as with methanol. Flexible fuel vehicles using fuel ethanol also have lower exhaust emissions than comparable gasoline vehicles.
    E-Ring: A hardened spring steel clip shaped vaguely like an "E"; more like a "C", but with a tab in the center. It is used on shafts & operating rods.
    EAIR: Electric Secondary Air Injection.
    EAP: Electric Air Pump.
    eB: early Bronco ('66-77).
    EB: 1) Eddie Bauer; 2) (slang) early Bronco.
    ECC: Electronic Control Computer. See EEC.
    ECM: Electronic Control Module. See EEC.
    ECU: Electronic Control Unit. See EEC.
    ECT[/URL]: Engine Coolant Temperature.
    Eddie Bauer: The most-luxurious trim level offered on Ford trucks from '85-96. Later models included matching leather luggage.
    EEC: Electronic Engine Control. AKA ECC, ECM, ECU, MCU, PCM, "brain", "computer", "controller".
    EEC-IV: Ford's fourth-generation EEC system; its first to incorporate on-board diagnostics (OBD) & memory to store diagnostic trouble codes (DTC[/URL]s). Their chips are soldered to their boards (meaning they can't be removed to change performance characteristics like some other manufacturers), but later versions include flash-programmable memory (EEPROM).
    EEC-V: Ford's fifth-generation EEC system, which incorporates the industry-standard OBD-II system.
    EEGR: Electronic EGR Valve; a motor-driven EGR with an integral position sensor.
    EEPROM: Flash Electrically Erasable Programmable Read Only Memory.
    EGO: Exhaust Gas Oxygen sensor, signal, or circuit. An early version of a HEGO/HO2S, without the heater.
    EGRT: EGR Valve Temperature Sensor.
    EGR Vacuum Regulator (EVR): A solenoid vacuum valve which controls vacuum to the EGR valve by a duty cycle (pulse) signal from the PCM. This, in turn, regulates EGR flow into the intake manifold. The EVR switches its output (to the EGR) between vent and manifold vacuum (through a reservoir).
    EGR Valve Position[/URL] (EVP): A sensor, signal, or circuit which reports how far the EGR valve has opened to the EEC. It mounts directly to the EGR and uses a pushrod to measure how far the diaphragm has lifted the pintle. Newer EGR systems don't use this sensor. Contrast EEGR, PFE, DPFEGR.
    EGT: Exhaust Gas Temperature
    EI: Electronic Ignition.
    Electric Air Pump (EAP): An electric pump used in EAIR systems.
    Electronic Distributorless Ignition System (EDIS): A system using an independent ignition module and one or 2 coil packs. AKA Integrated Ignition.
    Electronic Engine Control (EEC): The system or module that provides electronic control of engine (and often transmission) operation. AKA ECC, ECM, ECU, MCU, PCM, "brain", "computer", "controller". Contrast BCM, DDM, GEM, LCM.
    Electronic Ignition (EI): A system in which the ignition coil secondary circuit is dedicated to specific spark plugs without the use of a distributor. Ford has two types of EI systems, integrated EI and EI. EI is only used on the 3.0L Windstar and has a standalone Ignition Control Module (ICM). The Integrated Electronic Ignition (EI) System consists of a crankshaft position (CKP) sensor, coil pack(s), connecting wiring, and PCM. The Coil On Plug (COP) Integrated EI System uses a separate coil for each spark plug and each coil is mounted directly onto the plug. The COP Integrated EI System eliminates the need for spark plug wires but does require input from the camshaft position (CMP) sensor.
    Electronic Pressure Control (EPC): A solenoid valve, signal, or circuit which controls line pressure in the transmission.
    Electric Secondary Air Injection (EAIR): A pump-driven system for providing secondary air using an electric air pump.
    Electromagnetic Interference (EMI): Usually caused by ignition voltage spikes, solenoids, relay operation or noisy generator contacts.
    Electronic Pressure Control (EPC): A circuit or actuator which regulates hydraulic fluid pressure within an automatic transmission.
    Electronic Shift-On-the-Fly (ESOF): A system used to operate the of a 4WD or AWD vehicle while it is in motion.
    Electronic Variable Orifice Steering (EVO): A system or solenoid valve[/URL] which adjusts the level of assistance provided by the power steering system.
    E-Locker: An aftermarket electronically-selectable-locking differential produced by Eaton.
    Emissions Maintenance Warning module (EMW): A small module attached to certain '87-91 instrument clusters which can be safely deleted. Compare Combo, IMS. AKA EUL.
    End Of Line (EOL): A system designed specifically for use at assembly plants to make sure all new vehicles perform to design specifications.
    Endo: (slang) An end-over-end roll.
    Engine: A machine designed to convert thermal energy (typically derived from chemical energy in fuel) into mechanical energy to produce force or motion.
    Engine Coolant Temperature (ECT): A sensor, signal, or circuit which indicates the temperature of the engine coolant. It is typically installed in the heater core circuit, which is unaffected by the thermostat.
    Engine Fuel Temperature (EFT): A sensor, signal, or circuit which indicates the temperature of the fuel in the fuel rail.
    Engine RPM (RPM): A signal or circuit which indicates engine rpm.
    Engine RPM/Vehicle Speed Limiter: A strategy to prevent damage to the powertrain. The powertrain control module (PCM) will disable some or all of the fuel injectors whenever an engine rpm or vehicle overspeed condition is detected. The vehicle will exhibit a rough running engine condition, and the PCM will store a Continuous Memory DTC P1270. Once the operator reduces the excessive speed, the engine will return to the normal operating mode. No repair is required. However, the technician should clear the PCM and inform the operator of the reason for the DTC. Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice, etc. or excessive and sudden increase in rpm while in NEUTRAL or while driving.
    Environmental Protection Agency (EPA): a government agency which sets & enforces emissions standards in the US.
    Epoxy: A plastic formed by mixing several liquid or gel chemicals, which then harden. Most do not require air to cure, and will cure over a wide temperature range. Heat is usually produced by the curing process. Epoxies are commonly used as adhesives, sealants, paints, and structural repairs (JB Weld) because they are robust, durable, and rigid over a wide temperature range.
    Estate: See Wagon-Body.
    Ethanol: Grain alcohol; C2H5OH. An inexpensive fuel additive used to reduce cost and emissions. Blends containing more than ~15% ethanol require special engine management & fuel system materials. See E85.
    Ethylene Glycol: The most common antifreeze/antiboil agent in automotive coolant. It tastes sweet, but is extremely poisonous; attaching to the liver, it prevents normal toxins from being removed from the blood.
    EUL: See EMW.
    EVAP: Evaporative Emission system.
    Evaporative Emission (EVAP): A system to prevent fuel or other hydrocarbon vapors from escaping into the atmosphere. Typically includes a charcoal canister to store fuel vapors, a rollover valve on the fuel tank to prevent liquid fuel from entering the system, various airflow control solenoid valves, & the PCV system.
    EWP: Electric Water Pump.
    Exciter Ring: See Tone Ring.
    EXH HCV: Exhaust Heat Control Valve (carburetor/vacuum)
    Exhaust Gas Recirculation (EGR): A system which reduces NOx emissions levels by adding exhaust gas to the incoming air/fuel mixture, OR the valve used to regulate the flow of exhaust gas. The inert gas reduces combustion chamber temperatures, which not only reduce the formation of NOx, but also reduces the tendency to burn through Aluminum/alloy pistons.
    Exo-Cage: An external cage designed to protect a vehicle's body when off-roading. Most are primarily cosmetic, and not actually strong enough to work in an off-road rollover (which becomes more-likely as a result of the cage's weight) or an on-road collision. Contrast Family Cage; Nerf Bar; Rock Slider; Roll Bar; Roll Cage; Step Bar.
    Extreme Pressure (EP): a rating for chassis grease.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    F: Front
    F4E: F Level (119 lb-ft) 4 speed Electronic transmission.
    Fabricated: 1) assembled, as opposed to being a single piece; 2) welded-together, as opposed to being stamped or machined in 1 piece; 3) created locally from raw or common materials, as opposed to being mass-produced on a factory assembly line; 4) crude, as opposed to being professionally designed & built to modern standards.
    Fail-Safe Cooling Strategy (FSC): A strategy activated by the PCM only in the event that an overheating condition has been identified. This strategy provides engine temperature control when the cylinder head temperature exceeds certain limits. The cylinder head temperature is measured by the CHT sensor. Not all vehicles equipped with a CHT sensor will have the fail-safe cooling strategy. A cooling system failure such as low coolant, electric cooling fan failure, or coolant loss could cause an overheating condition. As a result, damage to major engine components could occur. Along with a CHT sensor, the fail-safe cooling strategy is used to prevent damage by allowing air cooling of the engine. This strategy allows the vehicle to be driven safely for a short time with some loss of performance when a overheat condition exist. Engine temperature is controlled by varying and alternating the number of disabled fuel injectors. This allows all cylinders to cool. When the fuel injectors are disabled, their respective cylinders work as air pumps, and this air is used to cool the cylinders. The more fuel injectors that are disabled, the cooler the engine runs, but the engine has less power. A wide open throttle (WOT) delay is incorporated if the CHT temperature is exceeded during WOT operation. At WOT, the injectors will function for a limited amount of time allowing the customer to complete a passing maneuver. Before injectors are disabled, the fail-safe cooling strategy alerts the operator to a cooling system problem by moving the instrument cluster temperature gauge to the hot zone and a PCM DTC P1285 is set. Depending on the vehicle, other indicators, such as an audible chime or warning lamp, can be used to alert the operator of fail-safe cooling. If overheating continues, the strategy begins to disable the fuel injectors, a DTC P1299 is stored in the PCM memory, and a malfunction indicator light (MIL) (either CHECK ENGINE or SERVICE ENGINE SOON), comes on. If the overheating condition continues and a critical temperature is reached, all fuel injectors are turned off and the engine is disabled.
    Failure Mode Effects Management (FMEM): An alternative vehicle operation strategy that protects vehicle function from the adverse effect of an EEC system failure.
    Family Cage: a style of Roll Cage with full-height protection for rear passengers.
    Fan: A device designed to supply a current of air, typically through a radiator, condenser, or transmission cooler. A fan may also have a frame, motor, wiring harness and the like. The term is typically applied to mechanisms which move air parallel to the fan's axis of rotation, and are distinguished from Blowers, which are typically centrifugal. Contrast air pump, air compressor.
    Fan Control (FC): A sensor, signal, or circuit for controlling the engine cooling fan.
    FC: Fan Control.
    FCIL: Fuel Cap Indicator Lamp
    FDM: Fuel Delivery Module[/URL].
    FEAD: Front End Accessory Drivebelt[/URL] system[/URL].
    Fender: The body panel above the front wheel or forward of the doors, distinguished from the Quarter Panel, which is behind the doors.
    FEPS: Flash EEPROM Programming Signal. 18 volt DC signal sent by the scan tool to initiate PCM reprogramming.
    FF: Flexible fuel.
    FFV: Flexible Fuel Vehicle.
    FIFO: First In First Out. A stock management pattern. Contrast LIFO, LILO, FILO.
    Fifth Wheel (5th Wheel): a common heavy-duty hitch system characterized by a round tiltable horizontal receiver (the fifth wheel) on the tow vehicle (tractor) and a vertical pin on the trailer; contrast Gooseneck. It is popular in heavy truck & large RV trailer applications.
    FILO: First In Last Out. A stock management pattern. Contrast LIFO, LILO, FIFO.
    Finite-Element Analysis: An engineering design process pioneered by Ford in the late 60s and first applied to a production vehicle on the Falcon Wagon. A physical part (which has nearly infinite elements in the forms of crystals &/or molecules) is simulated mathematically by a model containing a finite (MUCH smaller) number of elements, represented by triangles arranged as a web or wireform. The behavior of the part can then be calculated at various temperatures & load conditions to determine which elements are critical & which are expendable, thereby reducing the size & weight of the part, without reducing its strength, durability, or reliability. It is now an indispensible tool for nearly every engineering & physics discipline, and has altered industry almost as profoundly & abruptly as Ford's seminal contribution: the production line.
    FIPK: A popular aftermarket Open-Element air filter system by
    Firewall: The body panel between the engine bay & the passenger compartment.
    Fish-Tail: A driving maneuver (often accidental) accomlished by accelerating vigorously but briefly during a short turn that results in the back end of the vehicle whipping sideways, like a fish's tail.
    Fixed Yoke/Flange: A non-moving connection between a splined shaft (usually the output shaft of a transmission or transfer case) and a U-joint in a driveshaft. Broncos use a fixed yoke or flange on the t-case rear output.
    Flash Electrically Erasable Programmable Read Only Memory (EEPROM): An Integrated Circuit (IC) within the PCM. This IC contains the software code required by the PCM to control the powertrain. One feature of the EEPROM is that it can be electrically erased and then reprogrammed without removing the PCM from the vehicle. If a software change is required to the PCM, the module no longer needs to be replaced, but can be reprogrammed at the dealership through the DLC.
    Flathead: 1) A flathead (slotted) screw; 2) a flathead engine.
    Flathead Engine: An obsolete engine design distinguished by simple cylinder heads and valves within the block.
    Flathead Screw: A style of screw head using a simple, straight, central groove designed to be driven by a correspondingly simple, straight-edged tool. AKA Slotted . See Screw. Contrast Phillips, Torx.
    Flat-Rate or Flag-Rate: A common pay plan for automotive technicians, especially at a dealership. A comprehensive list of possible vehicle repairs is published (either by the manufacturer in the case of dealership & warranty repairs or technicians, OR by a 3rd-part company in the case of independent techs & customer-pay repairs) with specific descriptions of the tasks involved and the typical or allowable time to accomplish those tasks. Regardless of how long it actually takes the technician to complete the repair or the total cost billed to the vehicle owner, the tech is only paid for the published time. AKA "book time". Contrast "straight time" or "clock time".
    Flexible Fuel (FF): A system capable of using a variety of fuels for vehicle operation. These may include gasoline, diesel, biodiesel, ethanol, methanol, natural gas, propane, jet fuel, solar, or any combination.
    Flip: A roll onto the roof either end-over-end or sideways, or a barrel roll.
    Flop: A roll onto only one side (not onto the roof).
    FLTR: Filter (carburetor/vacuum)
    Fluorescent: The physical characteristic of a substance by which it converts absorbed radiation at one frequency (usually invisible) into a visible-frequency radiation (light). Most commonly, a mercury-vapor tube generates UV radiation, which is fluoresced into white light by the powdered phosphor coating inside the tube.
    FMEM: Failure Mode Effects Management.
    FMX: An early medium-duty automatic transmission derived from the FX/MX. It evolved into the AOD, AODE, 4R70W, and 4R75E.
    FoMoCo: An official abbreviation for Ford Motor Company, sometimes stamped into low-trim parts such as police hub caps.
    Forced Induction: Any air intake system using mechanical devices to push air into the intake at higher-than-atmospheric pressure. Contrast N/A. See Turbocharger, Supercharger, Ram-Air.
    Four-Cycle: (slang) See Four-Stroke Cycle.
    Four-Stroke: (slang) See Four-Stroke Cycle.
    Four-Stroke Cycle: An engine operating system that involve 4 strokes of each piston to complete one combustion cycle (a version of the Otto combustion cycle). On the first stroke, the piston is forced up by the crankshaft toward an open exhaust valve to expel burned fuel. Near the top of that stroke, the exhaust valve closes & the intake valve opens. On the second stroke, the piston is drawn down by the crankshaft, creating a vacuum in the cylinder which pulls fresh air (and usually gasoline) in. Near the bottom of that stroke, the intake valve closes. On the 3rd stroke, the crankshaft pushes the piston up toward a closed combustion chamber, creating pressure in the cylinder. Near the top of that stroke, diesel may be injected or a spark plug may be fired. On the fourth stroke, the burning fuel in the chamber forces the piston down, transferring power to the crankshaft. Because 3 strokes consume power for each 1 that produces power, 4-stroke engines are inherently less powerful by weight & less thermodynamically efficient than 2-strokes. But they require less maintenance & produce fewer emissions.
    Four Valve (4V): Four valves, two intake and two exhaust, per cylinder.
    FP: Fuel Pump.
    FPDM: Fuel Pump Driver Module.
    FPM: Fuel Pump Monitor.
    FPR[/URL]: Fuel Pressure Regulator.
    FPRC: Fuel Pressure Regulator Control.
    Frame: The heavy structure to which all other major components of a cab-on-chassis vehicle are attached. Common types include ladder & X . Contrast Unibody, Monocoque.
    Frame Horn: The end of a frame rail where something may be attached, such as a bumper.
    Freeze Frame: A block of KAM containing the vehicle operating conditions for a specific time. Typically associated with a DTC. Erasing DTCs also erases all freeze frames. They will also be erased if KAM or KAPWR fails.
    FreonŽ: The DuPont name for R-12 CFC. See Refrigerant.
    Front End Accessory Drive (FEAD): A system of belts & pullies on the engine to transfer power from the crankshaft to various accessory devices.
    FS: 1) Fullsize; 2) for sale.
    FSA[/URL]:Field Service Action[/URL]. See Recall.
    FSC: Fail-Safe Cooling Strategy.
    FT: 1) (ft) foot (12 inches); 2) Finger-tight; 3) (slang) F*****g tight
    FTO: Filtered Tachometer Output; the IDM circuit for CCD TFI-IV ignition systems.
    ft-lb: foot-pounds; a measure of torque (typically used for ROTATING torque, as in engine output). 1 ft-lb = 1 lbf at 1 ft from the center of rotation = 2 lbf @ 0.5' = 10 lbf @ 0.1'...
    FTP: Fuel Tank Pressure.
    Fuel: Any combustible substance burned to provide heat or power. Typical motor vehicle fuels include gasoline, diesel fuel, propane, CNG, LPG, ethanol, methanol, kerosene, & nitromethane. Other types of fuel include hydrogen, oxygen, hydrogen peroxide, butane, coal, wood, Uranium...
    Fuel Delivery Module the assembly containing the fuel pump, pickup siphon, pickup screen, reservoir, shuttle valve, & level sender used in most '90-up Fords
    Fuel Injector[/URL]: See Injector.
    Fuel Pressure Regulator (FPR[/URL]): A vacuum-operated valve on or near the fuel manifold (rail) which regulates fuel pressure from the pump to the injectors.
    Fuel Pressure Regulator Control (FPRC): A sensor, signal, or circuit which controls the fuel pressure regulator. Used primarily to provide extra fuel during cold starts.
    Fuel Pump (FP): A pump used to deliver fuel to the engine, usually submerged in the fuel tank.
    Fuel Pump Driver Module (FPDM): A module that controls an electric fuel pump in response to a pulse-code modulated (PCM) signal from the EEC.
    Fuel Pump Monitor (FPM): A sensor, signal, or circuit which monitors operation of the fuel pump.
    Fuel Rich/Lean: A qualitative evaluation of air/fuel ratio relative to an ideal A/F ratio known as stoichiometry, or 14.7:1 for normal gasoline. In the EEC system, rich/lean is determined by a voltage signal from the HO2S. An excess of oxygen (lean) is indicated by anHO2S[/URL] voltage of less than .4 volts; a rich condition is indicated by an HO2S voltage of greater than .6 volts.
    Fuel Tank Pressure (FTP): A sensor, signal, or circuit which indicates the internal pressure of the fuel tank and the EVAP system[/URL].
    Full-Floating (FF) Axle: An axle assembly whose axleshafts bear no weight, and can therefore 'float' within the housing. Because the shafts only experience torsional stresses, it is considered stronger (less likely to break) than a Semi-Floating Axle. All steering axles are full-floating, but their outers can be semi-floating, as in some Jeeps. Most Portal Axles are full-floating. A full-floating axle can be easily identified by the presence of a spindle nut which retains the hub on the bearings, even if the axleshaft breaks.
    Fullsize (FS): a vehicle approximately 74" wide; distinguished from Midsize, Compact, Subcompact, and Heavy.
    Full-Width (FW): a part or assembly for a fullsize vehicle, but installed on a midsize or compact; usually an axle.
    Fuse: An electrical connection designed to melt at a specific current draw (Amperes), thus opening (turning off) the circuit and protecting the wires from melting or burning. Installing a fuse rated higher than original defeats the purpose of the fuse since the wiring will melt before the larger fuse. Contrast Fusible Link, Circuit Breaker.
    Fusible Link: A normal wire with special insulation designed to contain the heat, spark, and melted metal when the wire burns from excessive current draw. Fusible link wire is not rated in Amperes since its characteristics are less-obvious, but it is typically 4 gauges (AWG) smaller (higher number) than the circuit it protects. Although many vehicles now use MEGA or MAXI fuses where older vehicles used fusible link wire, replacing older fusible links with fuses is not recommended unless the rest of the wiring is upgraded to match the newer arrangement. Never replace a fuse with fusible link wire. In an emergency, smaller-gauge wire may be temporarily substituted for fusible link wire until an appropriate repair can be made. Contrast Fuse, Circuit Breaker.
    Orange - 22ga. - 0.35mm
    Gray - 20ga. - 0.5mm
    Blue - 18ga. - 0.8mm
    Black - 16ga. - 1.0mm
    Gray - 14ga. - 2.0mm
    Blue - 12ga. - 3.0mm
    Orange - 10ga. - 5.0mm
    Black - 8ga. - 8.0mm
    FWD: Front Wheel Drive. A powertrain system which delivers engine power to a differential in the front axle only. Contrast RWD, AWD, 4WD.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    G: fuel code for Gasoline.
    Garter Spring: A style of quick connection used on some fuel or A/C line fittings comprising 2 tubular fittings whose lips face each other. A coil spring fills the gap between the tubes, and interferes with the lips, preventing them from separating until the spring is pushed onto the inner (outward-facing) lip. Contrast Duckbill.
    Gap: The distance between a spark plug's ground & center electrodes. The gap determines the voltage at which the coil fires, so too large a gap can damage the coil. Too small a gap produces a small, cold spark, which results in incomplete ignition of the fuel, low power, & high HC & CO emissions.
    Gall: A specific type of wear between metal parts (usually rotating) in which a lack of lubricant combined with high force results in specks of liquid metal being pushed into balls which cut grooves into the parts and often lock them together.
    GE: fuel code for Bi-Fuel, Gasoline/Ethanol.
    Gear-Drive: An aftermarket all-gear replacement for a timing chain.
    GEM: Generic Electronic Module: a multi-function module used for courtesy lighting, windows & locks, chimes, etc. AKA BCM, BSM, CSM...
    Generator (GEN): A rotating machine designed to convert mechanical energy into electrical energy. AKA Alternator (a term trademarked by Chrysler Corporation). Early types used an external fan and remote voltage regulator; modern types use an internal fan and external or internal voltage regulator, sometimes controlled by the PCM to achieve more efficient charging & longer battery life, as well as to reduce the alternator load on the engine during peak demand. The basic generator chassis produces an AC voltage (usually around 18.5V max) which is rectified by high-current diodes to a rough DC voltage. This roughness is smoothed by the battery, which is critical to protecting modern electronics from voltage spikes which were acceptable in older vehicles. A modern vehicle should never be operated with the battery disconnected.
    Glasspack: An aftermarket muffler that uses fiberglass between its outer shell & a perforated inner pipe. Externally, it looks very similar to a Cherry Bomb, and is often painted a similar red. It is popular because it fails to muffle, but is still legal in most places.
    GM: 1) fuel code for Bi-Fuel, Gasoline/Methanol; 2) Grand Marquis; 3) General Motors Corporation.
    Gn: Green wire or vacuum line.
    GND: Ground.
    Gold Plated Pins: Some engine control hardware has gold plated pins on the connectors and mating harness connectors to improve electrical stability for low-current circuits and to enhance corrosion resistance. The EEC components equipped with gold terminals will vary by vehicle application. Damaged gold terminals should only be replaced with new gold terminals.
    Goose: A brief opening and closing of the throttle (Dynamic Response test).
    Gooseneck: a common medium-duty hitch system characterized by a trailer tongue that arches over a pickup truck's tailgate then drops to a ball mounted to the floor of the bed; contrast Fifth Wheel. It is popular in agricultural applications.
    Gov-Lock: An OE torque-biasing differential offered in GM trucks. It is very effective, but very delicate and has a history of exploding when overrevved.
    GPM: Grams Per Mile; Gallons Per Minute.
    GPS: Global Positioning System. A network of geostationary satellites, or a device used to monitor signals from those satellites, and calculate its own position from that data.
    Grade: 1) a categorization of strength, toughness, durability, heat resistance, & corrosion resistance of fasteners. AKA Material Class in metric fasteners; 2) a long inclined driving surface.
    Green State Vehicle: Formally known as California Emissions. A vehicle that is equipped with California on-board diagnostics.
    Grind: A slow abrasive noise, like driving slowly on rough pavement. See NVH.
    Grindbox: (slang) A manual transmission. Contrast Slushbox.
    Groan: A medium steady rumbling noise, like a continuous zipper. See NVH.
    Grocery-Getter (GG): A disparaging term for a vehicle that LOOKS like an SUV but actually isn't capable of off-roading, hauling, or towing. It may also be used for a vehicle capable of those activities, but not USED for them by its owner/driver.
    Gross Axle Weight Rating (GAWR): the maximum recommended load on a particular axle (front FGAWR or rear RGAWR).
    Gross Combined Weight Rating (GCWR): the maximum weight of the towing vehicle (including passengers, optional equipment, & cargo) plus the trailer (including optional equipment, water, & cargo).
    Gross Trailer Weight Rating (GTWR): the maximum recommended trailer weight while being towed (including optional equipment, water, & cargo).
    Gross Vehicle Weight Rating (GVWR): the maximum recommended vehicle weight (including passengers, optional equipment, & cargo). Modifying a truck with heavier axles REDUCES its GVWR by at least the weight difference of the new axles. The only way to get a higher GVWR is to buy a vehicle engineered that way.
    Ground (GND): An electrical conductor used as a common supply for electric circuits, and with a relative zero potential, generally connected to the (-) battery terminal. Electrons (which have a negative charge) flow out of this terminal, through the ground system, to electrical & electronic components which consume their energy, through fuses & control switches, and ultimately return to the battery (+) terminal. Some vehicles & accessories use a positive-ground wiring system.
    Ground Effect: 1) The phenomenon by which air at relatively low pressure captured between a vehicle & the ground tends to lift the vehicle; 2) (slang) automotive bodywork added to reduce the ground effect(1), such as a front air dam or side skirts.
    Ground Plane: A flat physical surface (usually the ground or the metal body of a vehicle) directly under an antenna used to reflect radio waves to or from that antenna. It must be electrically grounded to the antenna to work. The concept is almost identical to a fluorescent tube standing upright on a black surface. Without a reflector at the bottom end, ~1/2 its output would strike the surface & be lost; but with a ground-plane reflector, that energy is redirected up & out, where it can be used. The term applies primarily to CB antennae on vehicles, where the lack of a physical ground plane on one side of the antenna (due to the antenna being installed on the side of the vehicle) results in poor transmission/reception range on the side of the antenna with no ground plane.
    Grounding: 1) connecting one side of an electrical circuit to a common conductor (ground) to reduce the number of wires needed when many circuits have access to this common conductor (as the many circuits within a vehicle sharing the body &/or frame); 2) the unwanted mechanical connection between a noisy part & the passenger cabin of a vehicle. See NVH.
    Growl: A low steady rumbling noise, like a low note on an electric guitar. See NVH.
    GSS: Gear Select Solenoid
    GT: Grand Touring. A style of vehicle with a better power-to-weight ratio than contemporary vehicles, making it more suited to long-distance (high-speed) travel, especially in the mountainous regions of Europe, where it can easily overtake the slower local traffic.
    Gy: Gray wire or vacuum line.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    H: combustion code for Hybrid Electric; chemical symbol for Hydrogen.
    Hall Effect: A process in which current is passed through a small slice of semi-conductor material at the same time as a magnetic field to produce a small voltage in the semi-conductor. Compare Magneto-Resistive sensor[/URL].
    Halogen: A group of chemicals characterized by their ability to produce visible light when excited. They are often used in incandescent bulbs, but are also used in certain refrigerants for their other chemical characteristics.
    Hard Fault: A fault currently detected by the system.
    Hardware Limited Operating Strategy (HLOS): A mode of operation where the PCM replaces output commands with fixed values in response to certain PCM malfunctions. HLOS mode is used when the system fault(s) is too extreme for the FMEM mode to handle. In HLOS mode, all software operations have stopped and the processor is running on hardware control only. The default strategy for this mode has a minimal calibration strictly to allow the vehicle to operate until it can be serviced. NOTE: In HLOS mode, Self-Test codes will not be output.
    Harshness: Any momentary sensation that the driver finds objectionable. See NVH.
    HB: Hydro-Boost.
    HC: 1) Hydrocarbon.; 2) High Compression.
    HCA: Hot Cranking Amps: the maximum amount of current a 12V battery can deliver for 10 seconds at 80°F without falling below 7.2V . Compare CCA, CA, RC, Ah.
    HCF: Hydraulic Cooling Fan
    HCFD: Hydraulic Cooling Fan Drive

    HCV: Heat Control Valve (carburetor/vacuum)
    HD: 1) Heavy Duty; 2) Hot-Dipped galvanized.
    HDL: Headlamp.
    Head: See Cylinder Head.
    Header or Header Pipe: An exhaust manifold fabricated from bent tubing (as opposed to being cast), usually tuned to maximize scavenging from the combustion chambers, resulting in more power from the engine. The tubes converge at the collector, which includes a fitting to attach the exhaust system. Some are wrapped or coated to keep heat in so that surrounding components are not damaged. Compare Shorty, Long-Tube Header.
    Headlamp (HDL): A logical input to a module that indicates status of the headlamps.
    Heat Exchanger: Any device designed to transfer heat from one fluid to another, including the radiator, intercooler, ATF cooler, PSF cooler, engine oil cooler, heater core, & evaporator core. Contrast Heat Sink.
    Heat Gun: An electric torch, or hi-power hair dryer, used mainly for melting plastics & stripping paint.
    Heat Riser Tube: A small duct that transfers warm air collected from around the exhaust manifold into the intake system (generally on carburetors before the filter) to aid in fuel vaporization in extreme cold weather.
    Heat Sink: Any conductive mass designed to absorb & dissipate heat from other components, such as the finned Aluminum casting used for '92-96 TFI-IV ignition modules. A heat sink is distinct from a heat exchanger in that a sink transfers heat from a solid to a solid, and then slowly radiates the heat (at a lower temperature) to a static fluid.
    HEAT VLV INT: Heat Valve Intake (carburetor/vacuum) regulates flow from the exhaust manifold shroud through the heat riser tube to the intake system. AKA Heat Riser Valve
    Heated Exhaust Gas Oxygen sensor (HEGO): An Oxygen Sensor (O2S) that is electrically heated. AKA HO2S.
    Heated Oxygen Sensor (HO2S[/URL]): An Oxygen Sensor (O2S) that is electrically heated. AKA HEGO.
    HEGO: Heated Exhaust Gas Oxygen sensor.

    H.E.I.: High-Energy Ignition system.
    Heim: A popular brand of spherical rod end often used in suspension & steering modification.
    Helical Gears: An improved gear design using spiral teeth on circular gears with parallel axes. The advantages include less wear, less noise, more tooth contact, & constant effective radius (smooth output). The disadvantage is an axial load. They are commonly used in transmissions. Contrast Bevel, Herringbone, Hypoid, Spur, Worm.
    Herringbone Gears: A rare improvement on the Helical design in which each gear consists of 2 opposite-angle helical-cut tooth sets, which eliminates any axial load. They are sometimes used in transmissions. Contrast Helical, Bevel, Hypoid, Spur, Worm.
    Hex or Hexadecimal: a rare numbering system using sixteen possible characters (usually 0-9 and A-F) in each digit. 'Hexadeci-' means sixteen. Nine is '9'; ten is 'A'; twelve is 'C'; fifteen is 'F'; sixteen is '10'; seventeen is '11'; thirty-one is '1F'; thirty-two is '20'.
    HFC: 1) Hydrofluorocarbon. see Refrigerant; 2) High Fan Control.
    HFCF: High Fan Control Fault.
    HFP: High Fuel Pump.
    HHDE: Heavy Heavy Duty (gasoline, CNG, or FF) Engine.
    HHDDE: Heavy Heavy Duty Diesel Engine.
    HICV: Hot Idle Control Valve (carburetor/vacuum)
    HID: High-Intensity Discharge.
    High Fan Control (HFC): Controlling the high speed cooling fan.
    High Fuel Pump (HFP): An output circuit or signal from the PCM which controls the high speed fuel pump.
    High-Energy Ignition System (HEI): an ignition system capable of spark voltage &/or current higher than most early designs. It is largely a marketing gimmick, with no appreciable performance or reliability improvement over most stock DI systems. Spark energy may be increased by a more-efficient coil design that delivers more current through the spark, or a coil capable of higher spark voltage (though spark voltage is physically limited by plug gap, which is why it's a gimmick), or by multiple spark discharge per firing event. Contrast D.U.I.(1).
    High-Intensity Discharge (HID): A type of light bulb which uses high voltage to produce visible light in a manner similar to that of neon. They are much more efficient (less heat; lower current) than incandescent bulbs.
    High Pinion (HP): any differential designed for the pinion gear's axis to be above the ring gear's axis. Some require reverse-cut gearsets. The advantage is reduced driveshaft u-joint flex angles; the disadvantage is reduced oiling of the pinion gear & its bearings.
    High Steer: any modification of the steering linkage that results in the tie rod assemblies being higher above ground than stock. Most often, it involves re-cutting the tapers in the steering knuckles so the TREs can mount from above.
    High Swirl Combustion (HSC): A cylinder and piston configuration that causes swirling of the air/fuel mixture in the cylinder.
    Hi-Po: High Performance
    Hiss: A steady high noise, like an air leak from a tire. See NVH.
    Hitch: A system of mechanisms that joins 2 vehicles (usually a truck & a trailer) for highway towing. The most popular styles are ball, pintle hook/lunette ring, and 5th wheel. There are several types of ball hitch, including tongue and goose-neck. Ball & pintle hitches can be bumper-mounted, or receiver style. Common hitch receivers are built in 4 classes, based on load capacity, with Class III (2" square, 5Kip pulling, 0.5Kip carrying) being the most popular for light trucks. A hitch may also incorporate an anti-sway system &/or a weight-distributing system.
    HLA: Hydraulic Lash Adjuster.
    HLOS: Hardware Limited Operating Strategy.
    HO: High Output.
    HO2S[/URL]: Heated Oxygen Sensor.
    Hog Head: (slang) see Third Member.
    Hook up: 1) gain adequate traction; 2) connect with recovery equipment.
    Hot Soak: Period of time after an engine operates when its internal heat has not yet dissipated into the environment.
    HP: 1) HorsePower (usually lower-case); 2) High Pinion; 3) High Performance
    H-Pipe: a method of interconnecting the banks of a dual exhaust system in which a short tube is welded between the 2 main pipes to regulate & tune the pressure waves that cross between the banks. It is the most common factory type of dual exhaust.
    HSC: High Swirl Combustion.
    Hub: The tubular rotating flange containing wheel bearings to which brakes & wheels are mounted. See also Hub Lock.
    Hub Lock[/URL]: A mechanism for connecting a hub to an axleshaft, most often on the front suspension of a 4WD vehicle. They may be operated manually (the most common), pneumatically, electrically, mechanically, or automatically[/URL] (the 2nd most common). Although some name-brand aftermarket manual hub locks have achieved an elevated status, they are all virtually indistinguishable based on quality, durability, & warranty. The only noticeable difference is in the ease of operation of the selector knob. AKA (slang) Lockout, (slang) Locking Hub, (slang) Hub.
    Hubcentric: The characteristic of certain wheel & hub combinations that result in the wheel being held centered by the hub pilot, as opposed to being centered by the lug nuts. Contrast Lugcentric.
    Hum: A low varying noise, like a distant light airplane. See NVH.
    Hydraulic: any process, system, or mechanism which operates on the incompressibility of liquids.
    Hydraulic'ed or HydroLocked: A condition in which a piston engine has ingested a liquid into the cylinders, causing severe mechanical damage due to the fact that liquids cannot be compressed. It occurs most often when fording deeper than the air inlet duct, but can also occur from fuel flooding.
    Hydraulic Lash Adjuster (HLA): A mechanism similar to a (solid) lifter which uses engine oil pressure to automatically adjust the valvetrain. AKA Tappet.
    HydroBoost (HB)[/URL]: A trademark name for a hydraulic brake booster. Most use fluid & pressure from the power steering pump, but some use a dedicated belt-driven pump & fluid system, or a dedicated electric pump with a pressurized reservoir. Contrast Vacuum Booster[/URL].
    Hydrogen: A highly flammable gas element. Chemical symbol H.
    Hydrogen Cell: an extremely efficient electrical generator with no moving parts, powered by refrigerated (liquefied) Hydrogen & Oxygen, producing only electricity & water. Often used in spacecraft.
    Hydrogen Generator: An aftermarket or homemade device usually consisting of a glass jar containing water and a heating element (usually INcorrectly referred to as an electrode) with a hose leading to the intake manifold. Proponents suggest that the bubbles coming off the element are pure Hydrogen, and that the energy it adds to the combustion chamber is greater than that required to generate the electricity consumed by the device, making it economical. There is no scientific basis for this belief, and water cannot be hydrolyzed by a single electrode. Even those few with 2 electrodes that actually hydrolyze water are consuming more electricity than the engine produces as a result of the generator's activity, and are therefore reducing the overall efficiency.
    HydroLock: See Hydraulic.
    Hypoid Gears: A complex gear system using spiral teeth on non-intersecting non-parallel shafts. They combine the benefits of Helical gears with Bevel, but the teeth abrade each other. They are commonly used in axles. Contrast Bevel, Helical, Herringbone, Spur, Worm.
    Hz: Hertz. A measure of frequency in cycles per second.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    i: the standard engineering abbreviation for electrical current, measured in Amperes
    IAB: Idle Air Bypass; see IAC.
    IAC[/URL]: Idle Air Control.
    IAT[/URL]: Intake Air Temperature. AKA ACT
    ICM[/URL]: Ignition Control Module[/URL].
    ID: 1) identification; identifier; identify, 2) Inside Diameter
    IDI: Indirect Injection.
    Idle Air Control (IAC[/URL]): A pulse-modulated solenoid valve which controls throttle bypass air to help control engine idle RPM. AKA Bypass Air Idle Speed Control solenoid (BPA-ISC).
    IDM: Ignition Diagnostic Monitor.
    IFS: 1. Independent Front Suspension; 2.]Inertia Fuel Shutoff switch[/URL].
    IGN GND: Ignition Ground.
    Ignition: System used to provide high voltage spark for internal combustion engines.
    Ignition Control Module (ICM): The module that controls the ignition system.
    Ignition Diagnostic Monitor (IDM): A signal or circuit from the ignition control module to the EEC/PCM. Compare SPOUT.
    II: Integrated Ignition; see EDIS.
    IMRC: Intake Manifold Runner Control.
    IMS:Inferred Mileage Sensor[/URL]. Compare Combo, EMW.
    IMS-EUL[/URL]: Inferred Mileage Sensor/Extended Useful Life Module[/URL]. See Combo.
    IMT: Intake Manifold Tuning.
    Incandescent Bulb: The earliest type of electric light; it operates by passing current through a resistive filament within an inert gas, generating enough heat to maket the filament glow. The inert environment prolongs the life of the filament (usually Tungsten), and certain gases (halogens) accentuate the light produced. They are relatively inefficient & fragile. Compare HID, Fluorescent, LED.
    Independent Front Suspension (IFS) or Independent Rear Suspension (IRS): A suspension system which allows either wheel to travel without inducing travel in the opposite wheel. Most incorporate a linkage which partially defeats this function called an anti-sway bar. They have the advantages of lower unsprung weight, better handling, & a smoother ride, but the disadvantages of more complex & delicate construction, more wearing parts, and more expensive alignment. Contrast Solid Axle.
    Independent Shop: An auto repair business not associated with a vehicle manufacturer.
    Indexing: A procedure for installing spark plugs so that their ground electrodes all point the same direction within the combustion chambers, theoretically to produce smoother, more-reliable power from the engine by causing all chambers to experience precisely the same (and possibly the ideal) propagation of the flame front.
    Indirect Injection (IDI): A diesel cylinder head design in which the fuel injector pintle is recessed in a pocket outside the combustion chamber.
    Induction: 1) the process of moving air into an engine; 2) an electromagnetic process by which energy is transferred without physical contact. It is the basis for solenoids, motors, transformers, & induction heaters.
    Inertia: The physical tendency of a mass (an object) to maintain its current speed & direction (even if stopped) until acted on by an external force. Compare Momentum.
    Inertia Switch or Inertia Fuel Shutoff (IFS[/URL]): A safety system or device used on vehicles with an electric fuel pump that shuts off the fuel delivery system when activated by predetermined force limits.
    Inferred Mileage Sensor/Extended Useful Life Module[/URL] (IMS-EUL[/URL]): Sometimes referred to as 'Infrared Mileage...' due to a typo in the Haynes manual. See Combo.
    In-House: Repairs performed at the shop where the owner left the vehicle. Most jobs are this category. Contrast Sublet.
    Injection Pressure (IP): A sensor, signal, or circuit which indicates the pressure in the fuel rail.
    Injector[/URL]: A device for delivering metered pressurized fuel to the intake system or the cylinders. AKA fuel injector.
    INT MAN: Intake manifold - the source of vacuum (on gas engines) to all vacuum-operated devices (carburetor/vacuum)
    Intake Air: Air drawn through a cleaner, regulated by a throttle, and distributed to each cylinder by a manifold for use in combustion.
    Intake Air Temperature (IAT): A sensor, signal, or circuit which indicates the temperature of the intake air. It may be in a runner in the intake manifold[/URL], in the , or in the duct between them. AKA ACT.
    Intake Manifold Runner Control (IMRC): A system, signal, or circuit which controls airflow through runners in the intake manifold.
    Intake Manifold Tuning (IMT): Control of airflow through runners in a split intake manifold.
    Integral: Incorporated by design as a permanent feature of a part. Said of bellhousings, washers, differential carriers. Contrast Captive.
    Integrated Electronic Ignition (EI): An Electronic Ignition system that has the Ignition Control Module (ICM) integrated into the PCM.
    Integrated Vehicle Speed Control (IVSC): Cruise control system incorporated within the PCM, used primarily on diesels & vehicles with electronically-controlled throttle.
    Intercooler: A component or system designed to cool the intake air, which has been heated by forced induction. The removal of heat from the pressurized air going into the intercooler increases the air density, which improves combustion efficiency, engine horsepower and torque. On some gasoline engines, the system consists of an additional radiator in the grille, a reservoir (independent from engine cooling system), an electric water pump, a heat exchanger (intercooler) located in the lower intake manifold and tubing to interconnect these components. On most diesel engines, heated & pressurized intake air from the turbocharger outlet is routed to a heat exchanger in the grille forward of the radiator, and then back to the intake manifold(s).
    Intermittent: 1. A fault that may not be present or identifiable currently; 2. A wiper system or setting that pauses the motor to reduce smearing & noise.
    IP: Injection Pressure.
    IRS: Independent Rear Suspension.
    ISC: Idle Speed Control; see IAC.
    ISO: 1) International Standards Organization; 2) Isolate, Isolation; 3) In search of, wanted.
    IVR: Instrument cluster Voltage Regulator; a calibrated thermostatic switch that regulates power (not voltage) going to an older thermal gauge that still uses a sender designed for 6VDC systems.
    IVSC: Integrated Vehicle Speed Control.
    IVV: Thermactor Idle Vacuum Valve (carburetor/vacuum)
    IWE: Integrated Wheel End; a vacuum-operated hub lock & unit bearing system used on some '04-up Ford trucks.
    J-Nut: A stamped, formed, & hardened sheet metal nut that is J-shaped to slip over an edge. It provides a stronger threading surface for a bolt or screw than the material onto which it is installed. Unlike a U-nut, the male fastener passes through a hole in only one layer of the J-nut.
    Jamb Nut: A nut (usually thinner & harder than a standard nut of the same thread size) used to lock a sleeve or an adjacent nut on a threaded shaft by being tightened against it until both nuts bind.
    Jumper Battery: A portable 12V battery with cables & clamps capable of supplying over 120A to a vehicle. Most include an integrated 110VAC charging system and diagnostic charge indicator. Some may include flashlight, air compressor, inverter, radio, etc. AKA Booster Pack.
    Jumper Cables: A pair of heavy wires with a connector or clamps capable of supplying over 120A from one vehicle to another for the purpose of instantly starting the engine whose battery is weak, or for slowly charging a dead battery. Longer wires must be of heavier gauge to carry enough current. They may also be used for battery welding. Contrast Booster Cables.
    JY: Junkyard.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    Kanooter Valve or Kanuter Valve or Kneuter Valve: A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
    Keyless Entry (KE): A system using a keypad on the driver's door to allow operation of the PL, courtesy lights, & trunk. Contrast Remote Keyless Entry (RKE).
    Keep Alive Memory (KAM): A volatile portion of the PCM memory where (among other things) adaptive strategies & certain fault codes are stored. KAM must maintain power (KAPWR) even when the vehicle is not operating.
    Keep Alive Power (KAPWR): Dedicated, unswitched power circuit that maintains KAM. Disconnecting the battery for more than ~2min depletes the PCM's built-in backup KAPWR, and causes the KAM to be lost.
    Key On Engine Off Self-Test (KOEO): A test of the EEC system conducted by the PCM with power applied and the engine at rest. Only basic circuit functions are tested; not the logic of the outputs.
    Key On Engine Running Self-Test (KOER): A test of the EEC system conducted by the PCM with the engine running and the vehicle at rest. In addition to all KOEO functionality, KOER also checks the logic of certain signals to certain others. E.g., a high MAF reading with a low RPM will generate a KOER DTC.
    Keystone Clamp: A simple hose clamp comprising a strap loop with a flat-topped arch buckled into it. When the legs of the arch are crimped toward each other, the clamp tightens & the arch becomes a triangle, similar in shape to a keystone.
    Kip: thousand pounds; Kilo-pounds; x,000lbs.
    Knock: 1) The sharp metallic sound produced when two pressure fronts collide in the combustion chamber of an engine. It may be caused by hotspots in the combustion chamber (either from poor engine design, carbon buildup, or overheating), high compression, low octane numbered fuel, a lean condition, low oil pressure, valvetrain slack, ignition timing too far advanced (high BTDC), insufficient EGR flow, or incorrect spark plugs. It can cause severe engine damage, including burning through pistons, valve or head damage, overheating, catalyst damage, exhaust leaks, ruptured head gaskets, or backfire (and that resulting damage). AKA Valve Clatter, Dieseling, Preignition, Detonation, Pinging. 2) Any heavy repeating sound, like brick falling on pavement.
    Knock-Off: 1) (slang) a cheap copy; 2) a style of wheel retained on the axle by a single central nut designed to be loosened by striking a wing with a lead hammer, common on antique cars.
    Knock Sensor (KS): A peizolectric sensor installed in the engine block which detects any vibration similar to engine knock. According to some Ford engineers, it causes worse performance than it prevents. If unplugging it causes a code, unscrew it from the block, reconnect it, and tape it to the harness so it can't touch anything metallic.
    KOEO: Key On Engine Off.
    KOER: Key On Engine Running.
    KPA: Kilopascal. Metric unit of pressure. 3.386 kPa = 1 inch of mercury (Hg.).
    KPH: Kilometers Per Hour. Metric unit of speed. 1.6 KPH = 1 MPH; 0.6 MPH = 1 KPH.
    KS: Knock Sensor.
    Ksi: thousand psi; Kilo-pounds per square inch; x,000 psi.
    L: 1) Liters. Metric unit of volume; 2) Left, from the operator's perspective while the vehicle is in motion; 3) Lightning.
    Ladder Frame: The most common style of frame consisting of 2 parallel members (frame rails, roughly horizontal) running the full length of the vehicle, and connected by perpendicular members (crossmembers). The rails & crossmembers may be channels or tubular (boxed). Contrast Unibody, Monocoque, Subframe.
    Lake Pipes: A popular brand of sidepipe, offered as OE on some vehicles like the '67 Corvette L88.
    LB: 1) Light Blue wire or vacuum line; 2) (lb) librae (Latin) = pounds
    lbf: pounds force, distinguished from lbm (pounds mass).
    lb-ft: pound-feet; a measure of torque (typically used for STATIC torque, as in tightening fasteners). 1 lb-ft = 1 lbf at 1 ft from the center of rotation = 2 lbf @ 0.5' = 10 lbf @ 0.1'...
    lbm: pounds mass, distinguised from lbf (pounds force).
    LCD: Liquid Crystal Display.
    LCM: Lighting Control Module - an electronic component that controls vehicle lighting, inside & out.
    LCV: EGR Load Control Valve (carburetor/vacuum)
    LD: Light Duty
    LDDT: Light Duty Diesel Truck.
    LDT: Light Duty (gasoline, CNG, or FF) Truck.
    LDV: Light Duty (gasoline, CNG, or FF) Vehicle, generally passenger cars and light trucks under 6000 pounds GVWR.
    Leakdown Test: a specialized test of a cylinder's ability to hold pressure. Compare Compression Test.
    Lean: 1) a fuel/air mixture that has more air than is necessary for the fuel to burn. In gasoline engines, it results in slightly more power, but also excessive heat and a tendency to detonate rather than burn. The excess heat also leads to the formation of NOx, oxidation of Aluminum pistons & heads, and overheating. In diesel engines, the engine runs cooler & makes less power. Contrast Rich. 2) a side tilt, as viewed from front or rear.
    LED: Light-Emitting Diode
    LED Display: A digital electronic display consisting of an array of LEDs, used to generate characters, symbols, & patterns. Very large displays using several colors of LED can be used to create video displays, such as on blimps. Contrast LCD, VFD.
    LEV: Low Emission Vehicle.
    LFC: Low Fan Control.
    LFP: Low Fuel Pump.
    LG: Light Green wire or vacuum line.
    LHD: Left-Hand Drive.
    LHDE: Light Heavy Duty Engine.
    LHF: Left Hand Front, from the operator's perspective while the vehicle is in motion.
    LHR: Left Hand Rear, from the operator's perspective while the vehicle is in motion.
    LHS: Left Hand Side, from the operator's perspective while the vehicle is in motion.
    LIFO: Last In First Out. A stock management pattern. Contrast LILO, FIFO, FILO.
    Lift: 1) Any modification that raises a vehicle's ride height, measured at the top of the arch above each wheel. See: Tire Lift, Suspension Lift, Body Lift; 2) A machine to raise an entire vehicle off the ground for service.
    Lifter: An engine part which rides against a cam lobe and operates a pushrod, rocker arm, or valve (directly). Most rotate to reduce wear, and some are hydraulically adjusted. Some have a roller that rides against the cam lobes to reduce friction. AKA Tappet, HLA.
    Light-Emitting Diode: An electronic device which uses semiconductor material to generate light. They are very efficient (very little heat compared to the light output) and have extremely long lifespans. Contrast Incandescent Bulb. See LED Display.
    Light Truck: A truck with a nominal cargo capacity less than 2 tons. Contrast Convertible, Coupe, Pickup, Roadster, Sedan, Van, Wagon-body.
    Lightning: A high-performance option package created by Ford SVO/SVT for F150 XLTs including (among MANY other things) the largest 1/2-ton engine for the given model year & a monochromatic paint scheme either in black, red, or white with "Lightning" logos inside & out. Only one Lightning Bronco was produced for a Ford executive. Compare Custom, XL, XLS, XLT, XLT Sport, Nite, Eddie Bauer.
    LILO: Last In Last Out. A stock management pattern. Contrast LIFO, FIFO, FILO.
    Limited-Slip Differential (LSD or L/S): A type of differential which uses constant friction in an attempt to keep both outputs turning at the same speed, while still allowing true differentiation when necessary. Contrast Open Differential, Locker, Torque-Biasing Differential, Spool.
    Lincoln-Locker: An OE open differential which has been welded solid, into a spool. It is named for the popular brand of welding machine. If done incorrectly, the axleshafts can never be removed, OR it can shatter during extreme use.
    Liquid Crystal Display (LCD): A digital electronic display which uses a thin layer of liquid crystal between layers of glass, and behind a polarizing filter. Transparent electrical terminals are embedded in the liquid layer so that, when a voltage is applied, the crystals polarize the light passing through them. The interaction between the crystals & the polarizing filter results in some areas of the display being black while others remain transparent. LCDs do not generate light, but can be placed in front of reflectors or lights to increase contrast. Common applications include pocket calculators, wristwatches, digital wall clocks, & certain computer monitors and TV screens. The effect is that characters or images can be generated in the shapes of the terminals in the display. Contrast LED, LED Display, VFD.
    Liquid Wrench: a brand name of penetrating oil.
    LLT: Limited LifeTime warranty.
    LNG: Liquified Natural Gas. See Natural Gas. Compare CNG; contrast LPG.
    Locked: 1) equipped with a locking differential (or several); 2) (fasteners) prevented from turning &/or loosening due to vibration or load; contrast Seized.
    Locked up: 1) (engine) seized; 2) (differential) see Locked.
    Locker or Locking Differential or Full-Locker: A mechanism which replaces the standard differential carrier and semi-permanently connects 2 output shafts (as in a differential) using springs & meshed teeth, but no gears. It does not provide true differentiation, but does allow the shafts to rotate at different speeds under certain conditions. The most popular is the Detroit Locker, now owned by Eaton. Contrast Selectable Locker, Mini-Locker, Open Differential, Limited-Slip Differential, Torque-Biasing Differential, Spool.
    Locking Hub or Lockout: (slang) See Hub Lock.
    LOF: Lube, oil, & filter.
    Long Block: An engine assembly consisting of a cylinder block, a crankshaft, all the bearings, all the connecting rods, all the pistons and rings, all the cylinder heads, a camshaft, timing gears/chains/covers, the assembled valvetrain, & most of the seals. Some also include an oil pump, an oil pan, a water pump, an intake manifold, a distributor, & a gasket set. Contrast Short Block, Smallblock, Bigblock.
    Long Term Fuel Trim (LONGFT1 and 2): While the engine is operating in closed loop fuel, the short term fuel trim corrections can be 'learned' by the PCM as long term fuel trim corrections. These corrections are stored in keep alive memory (KAM) in tables that are referenced by engine speed and load (and by bank for engines with two HO2S sensors forward of the catalyst). Learning the corrections in KAM improves both open loop and closed loop air/fuel ratio control. Advantages include: short term fuel trim does not have to generate new corrections each time the engine goes into closed loop; and, long term fuel trim corrections can be used both while in open loop and closed loop modes. Long term fuel trim is represented as a percentage, just like short term fuel trim, however it is not a single parameter. There is a separate long term fuel trim value that is used for each rpm/load point of engine operation. Long term fuel trim corrections may change depending on the operating conditions of the engine (rpm and load), ambient air temperature and fuel quality (% alcohol, oxygenates, etc.). When viewing the LONGFT1/2 PID(s), the values may change a great deal as the engine is operated at different rpm and load points. The LONGFT1/2 PID(s) will display the long term fuel trim correction that is currently being used at that rpm/load point.
    Long-Tube Header: A header whose collector is below the oil pan or outside the frame rails. See Header. Compare Shorty.
    Low Fan Control (LFC): Controlling the low speed cooling fan.
    Low Fuel Pump (LFP): An output circuit or signal from the PCM which controls the low speed fuel pump.
    LPG: Liquified Petroleum Gas. See Natural Gas.
    L/S or LSD: Limited-Slip Differential.
    LT: Light Truck; a truck in the 1/2- to 2-ton cargo range between 72 & 80" wide with a ladder frame.
    LUBR: Lifted Uncut early BRonco.
    Lug: 1) A lug nut or bolt; 2) Poor engine performance characterized by low RPMs, low torque at the wheels, high fuel consumption, pronounced exhaust & intake noise, and poor throttle response.
    Lug Bolt: A bolt that holds a wheel on a hub.
    Lug Nut/Lugnut: A nut that holds a wheel on a hub.
    Lugcentric: The characteristic of certain wheel & hub combinations that result in the wheel being held centered by the lug nuts, as opposed to the hub pilot. Contrast Hubcentric.
    Lunchbox Locker: A simplified type of aftermarket locking differential which only requires replacing the internals; not the entire carrier. They are considered weaker for several reasons. AKA Mini-locker.
    Lunette Eye: a heavy-duty hitch system characterized by a large cast-steel ring (the eye) gripped by a pintle hook. It is popular in US military applications, and for tandem heavy truck trailers.
    LVW: Loaded Vehicle Weight, defined by Curb Weight + 300 lbs.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    M: fuel code for Methanol
    M5HD: ZF S5-45 M5OD-HD manual 5-sp OD heavy-duty transmission.
    M5OD: A designation for 3 distinct manual transmissions: the Mazda M5OD-R1 used in mid-sized trucks; the Mazda M5OD-R2 (M5OD-LD) used in fullsize light trucks; and 2 similar ZF models:the S5-42[/URL] (M5OD-LD) & the S5-45[/URL] (M5OD-HD, or M5HD) used in fullsize heavy-duty light trucks. All have an Aluminum case with integral bellhousing, and were available in 2- or 4WD configurations. The Mazdas are considered unreliable and are commonly referred to as "Mazdog". The ZF, though not without its own problems, is highly sought-after as an upgrade transmission; particularly the 4WD versions.
    M85: Fuel containing 85% methanol alcohol. Fuel methanol (M85) is a mixture of approximately 85% commercial grade methanol (M100) and 15% unleaded gasoline. The resulting fuel has a higher octane rating than unleaded regular gasoline, allowing engine designs with higher compression and corresponding greater engine efficiency and performance (power). Winter blends may contain up to 30% unleaded gasoline to enhance cold engine starts, hence the sometimes-used M85-M70 designation. Severely cold weather may require additional measures for reliable starting. Methanol corrodes some metals and may cause some plastic
    and rubber components to swell, break down or become brittle and crack, especially when mixed with gasoline. Special materials and procedures have been developed for vehicles and the dispensers used by M85 fuel providers. Since methanol has less energy per gallon, fuel economy in miles per gallon will decrease as the percentage of methanol goes up. However, the FFV uses more of the energy available in the fuel when running on M85-M70 than on gasoline. Flexible fuel vehicles burning fuel methanol have lower exhaust emissions than comparable gasoline vehicles.
    M/T: Manual Transmission/Transaxle.
    MacPherson Strut: A combined suspension mechanism, incorporating a coilover shock (sometimes as a replaceable cartridge on early versions), an upper pivoting mount, and a rigid lower mount that attaches to a spindle or steering knuckle. It is commonly used on front-wheel-drive & unibody vehicles to save weight & complexity, at the expense of ruggedness and replacement costs. This design eliminates the need for an upper control arm, due to the strut's rigid lower mount controlling the spindle/knuckle in all angles except steering. Contrast Coilover Shock.
    MAF: Mass Air Flow.
    MAF RTN: Mass Air Flow Return.
    MagnaFlux: A process using electromagnetic induction & powdered iron dust to detect flaws in magnetizable parts. The dust particles collect near fractures, making them easier to identify, evaluate, &/or repair.
    Malfunction Indicator Lamp (MIL): A required on-board indicator to alert the driver of an emission related malfunction. May read either 'CHECK ENGINE' or 'SERVICE ENGINE SOON.' Compare CEL, SES.
    Mall-Crawler: a vehicle apparently well-equipped for extreme off-roading (or its owner), but meticulously clean & undamaged, indicating total lack of such use. AKA Poser.
    MAN VAC: Manifold Vacuum[/URL] (carburetor/vacuum). Measurement can yield valuable diagnostic information about the engine.
    Manifold: A device designed to collect or distribute a fluid, like air, exhaust, coolant, or fuel.
    Manifold Absolute Pressure (MAP): A sensor which detects the absolute pressure of the intake manifold air.
    Manual Lever Position Switch (MLPS or MLP): A sensor, signal, or circuit which indicates the selected drive modes of the transmission. AKA NSS, PNP, TR, DTR.
    MAP: Manifold Absolute Pressure.
    Marvel Mystery Oil[/URL] (MMO): An aftermarket brand of fluids; particularly, an oil/fuel additive that looks similar to ATF.
    Mass Air Flow (MAF): A system or sensor which provides information on the mass flow rate of the intake air to the EEC/PCM for engine management. Modern MAF sensors use a heated wire near a temperature sensor, and sometimes incorporate the ACT. A hot-wire MAF requires the EEC to measure the current flow needed to keep the MAF temperature sensor at a given temperature. The more air moving past the hot wire, the more current required to maintain the temperature. Early MAFs measured the position of a spring-loaded door; more air pushed the door farther out of the airstream.
    Match Mounting Tires: A technique used to reduce radial runout and tire spring rate on tire and wheel assemblies. Excessive runout is a source of ride complaints and match mounting can be used to minimize the runout. There are two ways to use match mounting: positioning of the tire on the wheel and positioning the wheel on the hub.
    1. Measure the total indicated runout on the center of the tire tread rib, and record it. Mark the tire and rim at the center of the tread rib, and record the reading. Mark the tire at the location of the valve stem for reference.
    2. Break down the tire and remount it 180 degrees on the rim so that the valve stem reference mark is opposite of the valve stem on the wheel.
    3. Reinflate the tire and measure the total indicated runout, and again mark the high spot.
    4. If the runout is reduced to acceptable guidelines the tire is ready to be put back into service. If the runout is still excessive, one of the following steps must be performed:
    * If the high spot is within 100mm (4 inches) of the first high spot on the tire, and is still outside of guidelines, replace the tire.
    * If the high spot is within 100mm (4 inches) of the first high spot on the wheel, the wheel may be out of tolerance, check the wheel for runout.
    * If the high spot is not within 100mm (4 inches) of either original high spot of the tire and rim, then draw an arrow from the second high spot to the first high spot (in the shortest direction) and rotate the tire on the rim 90 degrees in that direction. This will normally reduce the runout to an acceptable level.
    In the majority of cases, the first 180-degree turn of the tire will either fix the problem or indicate which item to replace.
    Mass Air Flow Return (MAF RTN): A return (ground) circuit for the MAF sensor signal.
    MayPops: (slang) cheap or treadbare tires.
    MC: Master Cylinder; the input device for a manual (pedal) hydraulic system. Commonly used in hydraulic brake & clutch systems, sometimes sharing a reservoir. See Slave Cylinder.
    MCU: Motronic Control Unit. See EEC.
    MD: Misfire Detection.
    Mechanical Secondary Air Injection: A pump driven system for providing secondary air using a belt driven pump. Contrast Pulse Air Injection System & Electronic Secondary Air Injection.
    Methanol: Wood alcohol; CH3OH. An inexpensive but poisonous fuel additive used to reduce the cost of fuel, and emissions. Blends containing more than ~5% methanol require special engine management & fuel system materials. See M85.
    MFI: Multiport Fuel Injection.
    MFS: Multi-Function Switch.
    MHDDE: Medium Heavy Duty Diesel Engine.
    MHDE: Medium Heavy Duty (gasoline, CNG, or FF) Engine.
    Microprocessor: A digital processor on a chip which performs logical operations on data.
    MIL: Malfunction Indicator Lamp.
    Military Wrap: A method of reinforcing a leaf spring pack by wrapping the 2nd leaf around the eyes on the 1st leaf. If the 1st leaf's eye fails, the 2nd wrap secures the pack to the vehicle temporarily.
    MilSpec: Military Specifications; a stringent set of design standards for almost any part or material.
    Mini-Locker: An aftermarket part which replaces the contents of an open differential carrier with a spring & tooth mechanism to semi-permanently lock the outputs together. Contrast Locker (Full-Locker).
    Mini-Spool: An aftermarket part which replaces the contents of an open differential carrier in order to lock the outputs together. Contrast Spool (Full-Spool).
    Minivan: A midsize passenger van under 5000lbs GVWR, generally unibody FWD.
    Mint: a vehicle that has been returned to its original condition, as it might have appeared on a dealer's lot after being prepped for delivery.
    Misfire (Miss): Any event in the cylinder that causes a sudden change (decrease) in the speed of the crankshaft.
    Misfire Detection (MD): Circuitry designed to detect a misfire by monitoring changes in acceleration of a wheel mounted on the crankshaft through a CKP.
    MLP or MLPS: Manual Lever Position Switch. See also DTR.
    Modular: A Ford V engine family introduced in the early 90s in which each head and the block were considered "modules". It includes the 4.6L V8, 5.4L V8, 8.0L V10, 5.0L V8, & 6.2L V8.
    Module: A self-contained group of electrical/electronic components, which is designed as a single replaceable unit.
    Momentum: the quantity of energy carried by a moving mass, relative to some fixed point. High speed &/or mass results in high momentum.
    Monitor Box: An optional EEC system test device which connects in series with the PCM and its harness and permits measurements of PCM inputs and outputs.
    Monocoque: A lightweight style of vehicle construction used in early race cars & airplanes consisting of a stressed structural skin, to which all other components are attached. Contrast Unibody, Ladder Frame.
    Motor: 1. A device which converts electrical energy into rotating mechanical energy; 2. A device which converts vacuum into linear motion (vacuum motor); 3. An engine (slang)
    Mount: A mechanical connection that holds a major component to a vehicle's chassis, such as an engine mount (motor mount), transmission mount, or body mount. Most isolate the component's vibrations from the chassis with rubber &/or a viscous fluid (fluid mount), usually silicone grease or oil. Solid mounts are used in high-load appliacations where occupant comfort is less of a concern than absolute reliability, such as engine mounts for flat-track racers.
    MPG: Miles Per Gallon
    MPH: Miles Per Hour
    Muffler: A resonating chamber used to reduce sound emissions in an airflow, usually engine exhaust.
    Muffler Bearing: A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
    Multiport Fuel Injection (MFI): A fuel-delivery system in which cylinders receive fuel by individual injectors that are opened in groups (usually 2 'banks' which do NOT correspond to the cylinder banks of a V engine). Normally fuel is delivered to each cylinder once per two crankshaft revolutions in four cycle engines and once per crankshaft revolution in two cycle engines. Compare Sequential Multiport Fuel Injection; contrast Central Fuel Injection, Throttle-Body Fuel Injection.
    Multi-Function Switch (MFS): A switch that combines the functions of turn signal, hazard, beam select, flash-to-pass, wiper & interval, and sometimes cornering lamp control.
    Multiplexing: The process of communicating several messages over the same signal path. The increased number of modules on the vehicle dictates a more efficient method of communication. This process allows multiple modules to communicate with each other through the signal path (BUS+/BUS-). Modules communicate with the powertrain control module using Standard Corporate Protocol (SCP) which determines the priority in which the signals are sent. (See SCP.) Multiplexing reduces the weight of the vehicle by reducing electrical wiring.
    Mumford Link: A method of laterally locating an axle, consisting of 2 long bars attached either to the frame or axle at their far ends, and 3 more bars between them with 2 points of attachment. The system allows the axle to roll (sway) or to move straight up & down, but not laterally. Contrast Panhard Bar, Watts Link.
    MY: Model Year.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    NAAO: North American Automotive Operations.
    NATB: Nationa Auto Theft Bureau.
    Natural: A color of plastic without dyes or pigments: semi-transparent milky white or light brown.
    Natural Gas (NG): A system capable of using compressed or liquefied natural gas (CNG/LNG) or liquefied petroleum gas (LPG) as vehicle fuel.
    Naturally Aspirated (N/A): An unforced-induction system which allows air to flow into the intake manifold by atmospheric pressure alone. Contrast Forced Induction, Turbocharger, Ram Air, Supercharger.
    NC: 1) Normally Closed; 2) National Coarse threads
    NCP: Non Compliance Penalty.
    N/D Switch: Neutral/Drive Switch; see Neutral Start/Safety Switch.
    Nerf Bar: A medium-weight beam below the rocker panel designed to fend-off minor damage when a vehicle drives off-road, and also as a step. Contrast Step Bar; Rock Slider; Exo-Cage.
    Neutral Start/Safety Switch (NSS): A sensor, signal, or circuit which indicates the selected non-drive modes of the transmission. AKA MLP, MLPS, N/D Switch, PNP, TR, DTR.
    New, Old Stock (NOS): a category of part that is not 'new' in the sense that it might be 20 years old, but has never been installed, and is usually in OE packaging.
    NF: National Fine threads
    NG: Natural Gas.
    NIB: New, In the Box - a part or kit in the condition one would expect when buying retail.
    Nipple: a tubular fluid connector for a hose. Compare Zerk.
    Nite: A cosmetic option package above XLT for '89-92 F150s & Broncos including monochromatic black paint, blacked-out chrome, a body tape stripe that fades from blue to purple or pink to blue (depending on year), and matching upholstery. Compare Custom, XL, XLS, XLT, XLT Sport, Lightning, Eddie Bauer.
    NO: Normally Open.
    Noise: Any sound that the driver finds distracting or objectionable.
    NOS: 1) Nitrous Oxide Systems™, a division of Holley - the largest producer of automotive nitrous-oxide systems; 2) a nitrous-oxide system; 3) New, Old Stock; 4) common shield gas for welding 25% Argon 75% CO2.
    NOx: Oxides of Nitrogen; the main chemicals responsible for acid rain.
    NP 208[/URL]: A common early chain-driven 4WD (no internal differential) part-time 2-speed transfer case built by New Process Gear with a fixed front yoke output on the L side. The NP 208F variant was built for Ford trucks. It was replaced by the BW 1342 & 1356 beginning around 1986. Eventually all Ford fullsize 4WD light trucks got the 1356, including the F550 PSTD.
    NP 435[/URL]: A common 4-speed manual transmission built by New Process Gear, known for its robustness & durability, even when used in 5-ton trucks. Although no longer in production, it is still in use in many UPS delivery trucks, and is a popular swap for off-road vehicles.
    NPT: National Pipe Threads which are tapered near the tip to form a seal.
    NSS: Neutral Start/Safety Switch.
    NTSB: National Traffic Safety Board. A federal office which oversees many aspects of motor vehicles.
    Nut: A female fastener[/URL] that typically provides a pre-threaded hole for a screw or bolt. Machine-threaded nuts are generally hex-shaped. See Grade, U-Nut, J-Nut, Press-Nut.
    NVG: New Venture Gear; the new name for New Process.
    NVH: Noise, Vibration, Harshness[/URL]. A classification of vehicle concerns.
    NVRAM: Non-Volatile Random Access Memory; a type of RAM that doesn't require power to retain its data.
    O: 1) fuel code for Other; 2) chemical symbol for Oxygen.
    O-Pipe: A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive[/URL].
    O-Ring: A simple rubber ring used as a seal. Most have a round cross-section, but some are square, rectangular, or diamond. The term may also be applied to simple rubber seals molded into other shapes than "O".
    OASIS: On-line Automotive Service Information System; the Ford data network used by dealership technicians, service advisors, & parts.
    O.A.T.: Organic Acid Technology; a type ofengine coolant[/URL].
    OBA: On-Board Air; a compressed air supply system built into a vehicle, usually a compressor driven by the engine belt, usually with a storage tank. It may be a converted A/C compressor, a dedicated air compressor, or a remote electric compressor.
    OBD: On Board Diagnostic.
    OBD-I: (slang) A technically meaningless term commonly used for all types/brands/standards of electronic engine management systems before the OBD-II standard.
    OBD-II: A national (and now international) standard for automotive engine management, emissions control, and fault reporting systems required in the US since 1996. It allows a single scanner to connect to all makes & models of vehicles for the purpose of monitoring & diagnosing most operating aspects of the engine and associated electronic systems. Some scanners have substantially more capabilities than others, such as real-time monitoring or reprogramming the engine computer.
    OBS: Old Body Style
    OC: Oxidation Catalytic Convertor.
    OCBR:Oklahoma Classic Broncos[/URL] Roundup; the 2nd-largest early Bronco off-road event held annually, usually in September at the SuperLift ORV Park in Hot Springs, AR.
    OCIL[/URL]: Overdrive Cancel Indicator Lamp. AKA TCIL
    OCS[/URL]: Overdrive Cancel Switch. AKA TCS
    OCT ADJ: Octane Adjust.
    Octane Adjust[/URL] (OCT ADJ): A circuit or shorting connector (jumper) that alters engine strategy to compensate for changes in fuel octane rating.
    OE: Original Equipment. Parts installed on a vehicle at the factory. Contrast Direct-Replacement, Aftermarket.
    OEM: Original Equipment Manufacturer. The original producer of factory-installed parts.
    Offy: (slang) Offenhauser; a brand name of race engine & performance parts.
    OHC: Overhead Cam.
    Ohm: 1) a physicist who identified the fundamental relationship between voltage (V, Volts), resistance (Ω or R, Ohms), and current (i or A, Amperes) as V = R x i ; 2) the standard measure of electrical resistance; (slang) the procedure of testing resistance or continuity ("Ohming").
    OHV: Off-Highway Vehicle. AKA Off-Road Vehicle (ORV).
    Oil-to-Air (O2A): a heat exchanger such as a transmission, power steering, or engine oil cooler.
    OMV or DMV: Office/Department of Motor Vehicles. A state office which typically oversees & administers motor vehicle registration, titles, & driver's licenses.
    On Board Diagnostic (OBD): A system that monitors some or all computer input and control signals. Signal(s) outside of the predetermined limits imply a fault in the system or in a related system.
    One-of or One-Off: One-of-a-kind; an unusually-modified or fabricated part or system; strange; unconventional; unique. Contrast OE, Direct-Replacement.
    Open Circuit: A circuit which does not provide a complete path for current flow (Off, broken circuit). Contrast Closed Circuit.
    Open Differential: A differential which divides the input torque (engine) inversely to the amount of resistance on the outputs (traction). Contrast Limited-Slip Differential, Locker, Torque-Biasing Differential, Spool.
    Open-Element Air Filter: A popular style of aftermarket air filter that has no box to keep out underhood air. The common misconception is that the factory box somehow restricts airflow, and that removing the box will allow more air into the engine. Under certain conditions, it may; but durning most modes, the fact that warm underhood air is being consumed reduces the engine's power & efficiency. See CAI.
    Open Loop: A mode of PCM operation during which actator outputs are based on programmed information stored in ROM. The PCM always starts in open loop until certain criteria are met, and many outputs are inactive during this mode. Contrast Closed Loop.
    Or: Orange wire or vacuum line.
    ORP: Off-Road Park.
    ORV: Off-Road Vehicle. AKA Off-Highway Vehicle (OHV).
    ORVR: On-board Refueling Vapor Recovery.
    OSS: Output Shaft Speed.
    OTA: Oil-To-Air fluid cooler (heat exchanger).
    Otto Cycle: The thermodynamic process (named for a German scientist) which takes place in most gasoline engines (reciprocating & Wankel; 2-stroke & 4-stroke). Contrast Diesel, Sterling, fuel cell.
    Output Shaft Speed (OSS[/URL]): A sensor, signal, or circuit which indicates the rotational speed of the transmission output shaft.
    Overbored: See Bored.
    Overhead Cam (OHC): An engine configuration that uses a single camshaft positioned above the valves.
    Overlay Card: A plastic card used with the monitor box to identify EEC signals for each engine. The card also programs the monitor box for auto mode measurements.
    OWL: Outlined White Letters; a style of tire sidewall design. See also RWL.
    Oxidation Catalytic Convertor (OC): A catalytic convertor system that reduces levels of HC and CO.
    Oxygen Sensor[/URL] (O2S): A sensor which detects oxygen (O2) content in the exhaust gases. Compare HEGO, HO2S.
    Ozone: A corrosive toxic blue gaseous form of oxygen (O3) formed naturally by electric discharge or high-altitude exposure to ultraviolet radiation. It blocks UV & other radiation from striking the surface of the Earth, but is broken down by many industrial chemicals including older refrigerants.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    PA: Public Address; a loudspeaker system, which (on vehicles) is typically connected to a CB radio or an emergency siren.
    PAG: 1) PolyAlkaline Glycol; an oil used in R-134a systems available in 3 viscosities: PAG-46 (all Fords), PAG-100 (most others, including most retrofit kits), & PAG 150. 2) Premier Automotive Group; Ford's collection of high-end subsidiaries including Lincoln, Volvo, Aston Martin, & until recently, Jaguar and Land Rover.
    Panel Van: A van with a 1-piece purpose-built body specifically suilted to its intended purpose, such as UPS delivery vans.
    Panhard Bar: A simple method of laterally locating an axle, consisting of a pivot on the frame, a parallel pivot on the axle housing (as far from the frame pivot as possible), and a nearly-horizontal bar between them. It allows the axle to roll (sway) or to move vertically, but not laterally. If the whole axle moves, it follows an arc and shifts toward the frame mount, which is the main drawback to a Panhard suspension. Leaf spring suspensions don't require any lateral control since the leaves provide that strength. AKA Track Bar. Contrast Watts Link, Mumford Link.
    PAnt: Power Antenna
    Parameter Identification (PID): Identifies an address in the PCM memory which contains vehicle operating information.
    Park/Neutral Position (PNP): 1) A sensor, signal, or circuit which indicates the selected non-drive modes of the transmission. AKA MLP, MLPS, NSS, TR, DTR; 2) A semiconductor configuration of positive-negative-positive. Contrast NPN.
    Particulate: Small solid matter found in exhaust gases, especially prevalent in diesel engines.
    PAS: Power Assisted Steering. See Power Steering.
    PATS: Passive Anti-Theft System. A factory anti-theft system which disables the fuel injector drivers if the code chip in the ignition key does not match the stored code.
    PC: Passenger Car.
    PCM: Powertrain Control Module. AKA ECC, EEC, ECM, ECU, MCU, "brain", "computer", "controller".
    PCV: Positive Crankcase Ventilation.
    PCV Valve: A replaceable gravity- & flow-controlled 1-way metering valve in the PCV system. Because it is exposed to crankcase sludge, it will fail if not replaced regularly. Its failure can result in engine fires, diluted or contaminated engine oil, accelerated wear throughout the engine, poor economy, DTCs, increased emissions, and NVH.
    P/D MTR: Park/Decelerate vacuum Motor; AKA Dashpot (carburetor/vacuum)
    Pernickety or Persnickety: excessively precise in the usage & meaning of words (like I'm doing with this list).
    Perspicacious: easily understood; adept at explanation or teaching.
    Perspicuous: keenly observant; adept at understanding.
    Photochemical: The action of light on air pollutants which contributes to smog.
    Phillips Screw: A style of screw head using a specifically-shaped central cross recess (+) designed to be driven by a correspondingly specifically-shaped tool. It is easily confused with Frearson, JIS, PoziDriv, and others. See Screw[/URL]. Contrast Slotted Screw, Torx.
    PI: 1) Performance-Improved; a ~1996 revision to the head design of the 4.6L modular engine, standardized ~2001; often confused with 2) Police Interceptor (slang) (a badge on certain Crown Victorias with P71 options); 3) Police Interceptor[/URL], a 2011 Ford model.
    PIA: Positioned In Assembly - a notation for wiring & connectors
    Pickup or Pickup Truck: A light truck built on a ladder frame with a cab separate from its walled, but open-top cargo bed. Contrast Box Van, Convertible, Coupe, Panel Van, Roadster, Sedan, Truck, Van, Wagon-body.
    PID: Parameter Identification.
    Pigtail: An electrical connector with preinstalled terminals, each of which has a short wire attached. It is generally used to replace a damaged original connector, but may be used to add new systems.
    Ping or Pinging: 1) See Knock. 2) Any light repetitive sound, like a marble hitting a tile floor.
    Pinion: A small circular gear that drives another gear. Specifically, the axial gear of the hypoid set in an automotive axle.
    Pitman Arm: A steering mechanism which converts the rotating motion of the steering shaft into the horizontal movement of the tie rods. Contrast Rack & Pinion.
    Pk: Pink wire or vacuum line.
    PL: Power Door Locks
    PM: Power Mirrors
    PMGR: Permanent Magnet Gear Reduction starter motor.
    PNP: Park/Neutral Position switch. See DTR.
    PO: Previous Owner
    Polarity: A characteristic of a binary physical phenomenon, such as electricity (which can be polarized + or -) or a magnetic field (which can be polarized N or S).
    Polarity-Reversing Circuit: An electronic circuit used to drive a motor, which is capable of driving it either direction by means of reversing the polarity supplied to the motor. Examples include Ford power windows, power locks, power antennae, power seats, power mirrors, power adjustable pedals, & sunroofs. GM typically uses double-wound motors, which are heavier, bulkier, & less efficient, but require simpler switches & circuits to control.
    Polarized Light: Visible light which has passed through a polarizing filter, as is commonly found on LCD displays & polarized sunglasses. Once polarized, the light cannot pass through a 2nd filter unless the 2nd is aligned with the 1st. Any change in the alignment results in the light being further dimmed. If the 2nd is 90° offset from the 1st, virtually no light passes. Light is also polarized by LCD (which is how the LCD generates the black areas) or by reflection off glass or water (which is why driving & fishing sunglasses are sometimes polarized to eliminate the glare).
    Pole Shoe: A ferrous core within the winding of an electric motor which enhances the strength of the magnetic field. Some starter motors have a swinging pole shoe attached to a lever which acts as a solenoid to push the drive into the ring gear.
    Polished: A grinding & sanding process inside a manifold or head port to remove roughness from casting, and thereby improve airflow, power, & economy.
    Polyurethane: A resilient & durable thermoplastic polymer, often used for automotive bushings. It is noticeably tougher than traditional black vulcanized rubber, and is easily colored for cosmetic style.
    Port: An opening, usually in the intake/exhaust manifold gasket surface of the head where the manifold runners join it.
    Port Fuel Injection: See Multiport Fuel Injection.
    Portal Axle: An axle assembly whose outboard ends incorporate an offset drive mechanism, placing the majority of the axle's bulk ABOVE the centerline between the roadwheels. This creates a 'portal' between the wheels, allowing greater ground clearance. Some agricultural vehicles use portal axles (often with hydraulic drives); the UniMog truck uses solid portal axles; the HMMWV & Hummer (H1) use independent front & rear portal suspensions;MatTracks (TM)[/URL] create a portal configuration.
    Ported or Port-Matched: A grinding process that attempts to precisely match the shapes & contours of the intake & exhaust manifold runners, gasket openings, & head ports to improve airflow, and thereby improve power & economy.
    Ported Vacuum: (carb/vacuum) A vacuum supply from a partial-throttle position within a carburetor commonly used to control distributor vacuum advance. It is inactive at idle (no vacuum) but changes to full manifold vacuum during tip-in.
    POS: 1) Positive; 2) (slang) Piece of $#!+ .
    Posi: (slang) Positraction.
    Positive Crankcase Ventilation[/URL] (PCV): A system which forcibly draws crankcase emissions back through the engine where they are burned. The PCV valve regulates the amount of ventilating air and blow-by gas to the intake manifold, and prevents backfire from traveling into the crankcase. The PCV valve should be mounted in a vertical position. Sometimes incorporated with the evaporative emissions system.
    Positraction: A particular model of LSD used by GM. It is now owned & manufactured by Eaton.
    Potentiometer (Pot): An adjustable resistance component commonly used as a position sensor for rotatable shafts (Example: TP Sensor). AKA Variable Resistor
    Power Ground (PWR GND): The main ground circuit in the EEC system. Distinguished from signal ground (SIG RET) & case ground.
    Power Steering: A system which provides additional force to the steering mechanism, reducing the driver's steering effort. It most often incorporates a hydraulic pump[/URL] powered by the FEAD supplying pressure to a gear box[/URL] or rack. See also EVO.
    Power Steering Pressure (PSP): A sensor, switch, signal, or circuit which indicates the pressure in the power steering system.
    Power Take Off (PTO): 1. A mechanical connection for using engine power for aftermarket equipment such as hydraulic pumps, generators, & agricultural implements. 2. An EEC input signal used to disable On Board Diagnostic Monitors during PTO(1) use.
    Powertrain: See Drivetrain.
    Powertrain Control Module (PCM): The module that controls the EEC system. AKA ECC, EEC, ECM, ECU, MCU, PCM, "brain", "computer", "controller". Compare OBD.
    PPM: Parts Per Million. A measure used in emissions analysis.
    Preignition: See Knock.
    Prerunner: a vehicle built to run off-road race courses at high speeds, but that is much cheaper to build, repair, & operate than a full-on racer. Typically, it is a 2WD lifted truck with lightweight safety features and moderate handling improvements used by the race driver to test & learn the course.
    Press-Nut: A stamped, formed, & hardened spring steel nut without threads that slips over a smooth shaft & bites into it to provide retention. It is not designed to be removed intact, but often can be; especially if installed on a shaft whose surface is relatively hard.
    Pressure Feedback EGR[/URL] (PFE): A sensor, circuit, signal, or system that monitors EGR pressure with a single-port sensor. Contrast DPFEGR, EEGR, EVP.
    PRNDL or 'prindle': (slang) shift indicator.
    Profile Ignition Pickup (PIP): A sensor, signal, or circuit which provides crankshaft or camshaft position data for ignition synchronization.
    Programmable Speedometer/Odometer Module (PSOM[/URL]): A module that processes vehicle speed information for use in various electronic systems, displays speed on an analog face, and displays odometer data in a digital LCD. The PSOM can be programmed to accommodate various tire and axle combinations. It is unaffected by gear ratio changes.
    PROM: Programmable Read-Only Memory. ROM without program instructions.
    Prop Shaft or Propeller Shaft: See Driveshaft.
    Protocol: A set of rules for the exchange of information on a network.
    PSOM[/URL]: Programmable Speedometer/Odometer Module.
    PS: 1) Power Seats; 2) Power Steering; 3) Power Sunroof
    PSF: Power Steering Fluid; see ATF.
    PSP: Power Steering Pressure.
    PSTD: PowerStroke Turbo Diesel.
    PTFE: PolyTetraFluoroEthylene; the chemical name for TeflonŽ, a lubricating powder which is sometimes embedded in silicone rubber as a non-stick coating or polish, or in plastic tape as a pipe sealant. It may also be added to plastics, oils, & greases.
    PTO: Power Take Off.
    Pu: Purple wire or vacuum line.
    Pulse Width (PW): The length of time an actuator, such as a fuel injector, remains energized, measured in milliseconds or degrees. Compare Duty Cycle.
    Pulse Width Modulation (PWM): A signal pattern characterized by flat peaks of varying duration but constant height separated by an absence of signal (ground) which controls the intensity of an output by varying the signal duty cycle.
    Pump: A device used to raise, transfer, or circulate fluids at a relatively constant pressure. Contrast Compressor.
    Punch: 1) A tool or system for cutting holes in thin material without rotating the cutting surface; 2) (slang) a Drift.
    Purge Flow (PF): The quantity of fuel vapor burned in the engine.
    Push-Start: 1) a technique for starting an engine with a failed starting system, by pushing it up to a speed that will allow the transmission to spin the crankshaft. The minimum speed for an automatic is much higher than for a manual transmission; 2) an early style of TFI-IV ignition system that uses a black module. Contrast CCD.
    PVC: PolyVinyl Chloride; a common type of plastic. Often confused with PCV.
    PWR GND: Power Ground.
    Quarter or Quarter Panel: The body panel behind the doors, distinguished from the Fender or Wing, which is forward of the doors.
    Quick Test: A functional diagnostic test of the EEC system consisting of vehicle preparation and hookup, KOEO, KOER and Continuous Memory Self-Tests.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    R: 1) combustion code for Otto Cycle Rotary (Wankel) engines; 2) Red wire or vacuum line; 3) Rear, from the operator's perspective while the vehicle is in motion; 4) Resistance (see Ohm).
    R&I: Remove & Install - take a part/component out/off & then put it back in/on without repair. For example: when tires are simply rotated, that's R&I 4 wheels. Even if the part/component is being rebuilt, that's a separate job, so the R&I still applies.
    R&R: Remove & Replace - take a part/component out/off & put another in/on. For example: an oil change is an R&R of the oil & filter.
    RABS: Rear Antilock Brake System.
    Rack & Pinion: 1) A common gear system using a straight row of gear teeth (the "rack") and a circular gear in mesh (the "pinion") to convert the rotating motion of the pinion shaft into the linear motion of the rack; 2) A steering linkage using such a gearset. Contrast Pitman Arm.
    Radiator: The engine's liquid-to-air heat exchanger(s).
    Rag Joint: A type of u-joint consisting of 2 yokes attached to a fiber-reinforced rubber disk, used in steering and driveshafts. AKA Jured Coupling.
    Ram: A linear hydraulic actuator.
    RAM: Random Access Memory. Memory into which information can be written as well as read. It is typically volatile (does not survive power loss) and much faster than (nonvolatile) EEPROM.
    Ram Air: A forced-induction system which uses the vehicle's forward motion to create pressure in the intake manifold. Contrast Turbocharger, Supercharger, Naturally Aspirated.
    RAP: 1) Remote Anti-Theft Personality module; 2) Retained Accessory Power.
    Rap: to strike sharply to induce vibration, as when loosening or removing a stuck part.
    Ratchet: 1) a toothed mechanism that allows rotation in only one direction; 2) a wrench incorporating such a mechanism, typically with a square drive for sockets & other tools.
    Rattle: A quick irregular but continuous noise, like an ice-cream churn.
    RC: Reserve Capacity: the number of minutes a fully charged battery at 80°F can supply 25A without dropping below 10.5V. This indicates the actual amount of enenrgy stored in the battery. Longer time (or higher current) is better, and comes from larger, heavier batteries. Compare CA, CCA, HCA, Ah.
    Red Wrench: (slang) a torch, usually acetylene due to its reddish flame. See also Blue Wrench.
    Recall[/URL]: A program authorized by the manufacturer whereby a known fault or issue with a motor vehicle is repaired, usually without additional cost to the owner, & usually without expiration. A recall generally applies to a very specific group of vehicles, and the manufacturer identifies each VIN to the OMV of each state, which then furnishes the manfuacturer with the registered owner's name & mailing address. Recalls are generally overseen by NTSB &/or DOT, but are administered by the manufacturer. AKA FSA[/URL]. ContrastTSB[/URL].
    REDOX: Reduction/Oxidation Catalytic Convertor.
    Reduction/Oxidation Catalytic Convertor (REDOX): An advanced catalytic convertor system. At low temperatures, it reduces levels of HC and CO. At high temperatures, it also reduces levels of NOx.
    Reefer: (slang) a refrigerated semi-trailer.
    Reference Voltage (VREF): A dedicated circuit that provides a 5.0 volt signal used as a reference by certain sensors.
    Refrigerant: The working fluid in heat transfer systems that operate below ambient temperature. The most common refrigerant for mobile A/C is R-134a (SuvaŽDuPont), a non-chlorinated hydrofluorocarbon (HFC); older systems used R-12 (FreonŽDuPont), a chlorinated fluorocarbon (CFC) known to have several adverse environmental effects. Contrast Coolant.
    Refurbished: a part or system that has been brought back into nominal working condition, though not necessarily by the original manufacturer, or to original specifications.
    Regenerative Brakes: A system for slowing a moving vehicle which stores the energy, instead of simply converting it to heat as normal brakes do. Regenerative braking systems may use dynamos to store the energy electrically, air compressors or hydraulic pumps to store it as pressure, or other means. They are most commonly used on commercial & industrial vehicles which make frequent stops, like city buses.
    Relay: A generally electromechanical device in which a high-current (load) circuit is opened or closed by changes in a low-current (trigger) circuit. A common relay is an electromagnetically-operated switch, in which a small current passing through an electromagnetic coil pulls or pushes a steel slug or plate connected to a switch. Some act through a sealed glass bulb which may contain Mercury contacts. Other relays are solid-state & work similarly to transistors, but transistors' output is proportional to the input, and relays are on-off. Almost all Ford vehicles use a starter relay[/URL], and most are mounted to the right inner fender or wheelwell near the battery. Often confused with Solenoid.
    Relay Module (RM): A module containing two or more relays.
    REM: Rear Electronic Module.
    Remanufactured: a part or system that has been professionally returned to original working specifications, usually by the original manufacturer.
    Remote Anti-Theft Personality (RAP) Module: a module combining functions of earlier remote keyless entry, theft, and illuminated entry modules. Compare GEM. Contrast Retained Accessory Power.
    Repetitive Spark: Multiple firings of individual spark plugs at engine speeds below 1000 RPM to improve idle quality and improve emissions. AKA Multiple Spark Discharge (MSD) (TM).
    Restified: (slang) a vehicle that has been returned to working condition using much more modern parts & systems than it originally had, such as EFI in a 1960's vehicle.
    Restored: a vehicle that has been returned to its original condition, as it might have appeared a short time after being purchased.
    Retained Accessory Power (RAP): An optional feature that allows certain key-switched electrical systems to continue working with the key off for a limited time. Most cancel when a door is opened. Compare Battery Saver. Contrast Remote Anti-Theft Personality module.
    Return (RTN): A dedicated sensor ground circuit.
    RF: Radio Frequency. A band of electromagnet frequencies between ultrasonic & microwave.
    RFI: Radio Frequency Interference. A high-frequency form of EMI.
    RHD: Right-Hand Drive.
    RHF: Right Hand Front, from the operator's perspective while the vehicle is in motion.
    RHR: Right Hand Rear, from the operator's perspective while the vehicle is in motion.
    RHS: Right Hand Side, from the operator's perspective while the vehicle is in motion.
    Rich: a fuel mixture that contains insufficient air for the fuel to burn completely. In gasoline engines, it results in a cool-running engine, soot both in the exhaust stream and as deposits in the combustion chambers, HC emissions, CO emissions, reduced power, blow-by, oil thinning by fuel contamination, catalyst overheating, and reduced fuel economy. In diesel engines, the engine runs hot & makes more power. Contrast Lean.
    RITS: Run In The Sun; an off-road event for Bronco owners & their friends held each year in the SouthEast, usually organized by the webmaster of FourDoorBronco[/URL].
    RKE: Remote Keyless Entry - a system for operating the PL, trunk, &/or alarm via a radio-transmitter key fob. Some also allow remote starting. Contrast Keyless Entry (KE).
    RM: Relay Module.
    Roadster: An open passenger car with 2 doors, with or without a removeable/collapsible roof. Contrast Convertible, Coupe, Pickup, Sedan, Truck, Van, Wagon-body.
    Roar: A low steady continuous noise, like inside a cruising jet airliner.
    Rock Rash: (slang) Body damage due to contact with terrain while wheeling. AKA Environmental Streamlining.
    Rock Slider: A heavy beam below the rocker panel designed to carry the weight of the body over rocks when a vehicle drives off-road. Contrast Step Bar; Nerf Bar; Exo-Cage.
    Rocker or Rocker Arm: A lever in the head operated by the camshaft (possibly through lifters & pushrods) which opens the valve. Some have a roller to reduce friction.
    Rocker Panel: The body panel below the doors.
    Roller (Lifter or Rocker): A low-friction design of valvetrain using a wheel between the lifter & cam lobe, &/or between the rocker & valve.
    RON: Research Octane Number. The laboratory-measured octane number of an automotive fuel. Contrast actual octane number, nominal octane number.
    Routine: A group of related tasks, such as a series of diagnostic tests.
    Root-Mean Square (RMS): A mathematical operation to produce a useable value for signals whose average value is 0. Necessary for all AC signals, and generally calculated based on 60Hz. DMMs which specify 'RMS' on their packaging calculate it based on the actual measured frequency, and are therefore far more accurate for most automotive signals, whose frequencies often vary.
    Rotary: See Wankel.
    Rotor: the insulated conductor within a distributor.
    RPM: Engine Revolutions Per Minute.
    RTN: Return. AKA Ground.
    RTV: Room-Temperature Vulcanizing - a rubber that cures & crosslinks without additional heat, such as silicone rubber sealants.
    Rumble: A low heavy continuous sound accompanied by a vibration, like a skateboard on rough pavement.
    Run-on: A symptom experienced by carburetor engines in which the throttle plate(s) remain partially open after key-off, allowing enough air to continue to draw fuel into the dirty or overheated combustion chambers. The hot deposits or metal ignite the fuel mix without a spark, causing the engine to continue running, albeit roughly, & at a VERY low speed. This symptom is often confused with preignition. EFIs don't suffer from this because the injectors shut down at key-off.
    RV: 1) Recreational Vehicle; 2) Rear-View mirror.
    RWD: Rear Wheel Drive. A powertrain system which delivers engine power to a differential in the rear axle only. Contrast FWD, AWD, 4WD.
    RWL: Raised White Letters; a style of tire sidewall design. See also OWL.

  15. #15
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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    S: 1) Spark port (carburetor/vacuum) A nipple on a carburetor whose vacuum response is designed to control the vacuum advance of a distributor; 2) Stator terminal on an alternator or voltage regulator, ~1/2 B voltage when the alternator is working properly; 3) combustion code for Otto 4-Stroke-Cycle Piston engines.
    SAE: Society of Automotive Engineers, now SAE International[/URL].
    Safety Certification Label[/URL]: A sticker showing the manufacturer, build date, VIN, & other information needed to show compliance with vehicle safety laws & standards. It is most often applied in the driver's door jamb area, and usually contains a bar code version of the VIN. Some also indicate installed options & cargo capacities. AKA VIN Sticker, Door Jamb Sticker.
    Saloon: See Sedan.
    SAS: Solid Axle Swap
    SC: Supercharger or supercharged.
    Scan Tool (ST): A device that interfaces with the PCM and communicates information on a data link. Most can read codes and display them either as a flashing light, or as text. Some can read live data from the PCM. Very expensive models (usually factory-licensed) can retrieve &/or edit EEPROM data within the PCM and other modules.
    SCDS: Speed Control Deactivator Switch; the secondary (failsafe) cruise control cancel switch. An early type is the subject of a massive recall[/URL] due to fires.
    SCP: Standard Corporate Protocol.
    Screw[/URL]: 1) A typically light-duty fastener[/URL], generally with a recessed-drive head for wrist-operated tools, and often to be used in unthreaded holes. See Slotted, Phillips, Torx. Contrast Bolt. 2) (slang) An F150 SuperCrew (4-door short bed).
    Seat Cover: (slang) an attractive female passenger.
    Secondary Air[/URL]: Air provided to the exhaust system anywhere downstream of the exhaust valves.
    Secondary Air Injection (AIR): A pump-driven system for providing secondary air.
    Secondary Air Injection Bypass (AIRB): See TAB.
    Secondary Air Injection Diverter (AIRD): See TAD.
    Sedan: A passenger car with 4 doors. Contrast Convertible, Coupe, Pickup, Roadster, Truck, Van, Wagon-body.
    Seized: permanently un-turnable due to metal corrosion, deformation, or failure; contrast Locked (2).
    Selectable Locker or Selectable-Locking Differential: An aftermarket differential with a mechanism that can convert it to behave as a spool when the operator chooses. Contrast Open Differential, Limited-Slip Differential, Locker, Mini-Locker, Torque-Biasing Differential, Spool, Mini-Spool.
    Self-Clearancing: (slang) allowing moving parts (such as oversized tires) to wear against other parts (such as wheelwells & fenders) until there is no more interference.
    Self-Test: A general term for three distinct aspects of the EEC system Quick Test: Key On Engine Off, Key On Engine Running, and Continuous Memory. Compare OBD.
    SEMA: Specialty Equipment Market Association. A trade guild of businesses who supply non-OE vehicle parts, OR a trade show they host each year. Member businesses cooperate closely with automakers to develop high-quality aftermarket parts.
    Semi-Floating Axle: An axle assembly whose axleshafts bear the weight of the vehicle only at their outboard ends. Their inboard ends 'float' in the differential side gear splines. Contrast Full-Floating Axle.
    Semi-Truck: A truck built in 2 or more independent interchangeable sections: usually, a tractor containing the drivetrain, cab, & hitch; and a trailer for cargo or equipment.
    Sensor: The generic name for a device that senses either the absolute value or a change in a physical quantity such as temperature, pressure or flow rate, and converts that change into an electrical quantity signal[/URL]. A sensor is typically an analog device. Its digital counterpart is a switch.
    Sensor Ring: SeeTone Ring[/URL].
    Sequential Multiport Fuel Injection (SFI): A multiport fuel delivery system in which each injector is individually energized and timed relative to its cylinder intake event. Compare Multiport Fuel Injection.
    Servo: A remote actuator which can be regulated to a precise position, as opposed to simply an extreme of its range of motion. Common examples include cruise control servos, HVAC door servos, & power seat or power mirror motors WITH memory. Those without memory capability are simply motor-driven mechanisms, but do not qualify as servos.
    SES: Service Engine Soon light. See MIL.
    SFA: Solid Front Axle. See Solid Axle
    SFI: Sequential Multiport Fuel Injection.
    SFR: Single-Function Reservoir.
    Shackle Flip: a method of lifting a vehicle originally built with the shackle & bracket below the leaf spring.
    Shield: A conducting sleeve that surrounds wires to isolate them from electromagnetic interference (EMI).
    Shift Indicator Lamp (SIL): A lamp that indicates the preferred shift points for manual transmission/transaxle vehicles.
    Shift Solenoid (SS): A device that controls shifting in an automatic transmission.
    SHO: Super High Output.
    Shock: 1) the sensation of electricity passing through one's body; 2) a physical jolt, or sudden dramatic temperature change (thermal shock); 3) (slang) a shock absorber.
    Shock Absorber: The misnomer for a spring damper, typically gas-charged oil-dampened. The spring & suspension mechanism actually absorb the shock; the "shock absorber" merely slows the suspension & the spring's reaction to keep the tires in contact with the surface better.
    Short Block: An engine assembly consisting of a cylinder block, a crankshaft, all the bearings, all the connecting rods, all the pistons and rings, & few if any seals. Some also include a camshaft, timing gears/chains/covers an oil pump, an oil pan, & a gasket set. A short block does NOT include cylinder heads, valve covers, or intake manifold. Contrast Long Block, Crate Engine, Smallblock, Bigblock.
    Short Circuit: A connection between a circuit and any other point. While generally used to indicate an undesirable connection, all wires are short circuits between the terminals they connect. The expression 'short' indicates that there is very little resistance between the 2 points. The most common type is a short from power to ground, which results in extremely high current flow, causing fuses to burn, wires to melt, or fires to start. Contrast Open Circuit, high resistance, Off.
    Short Term Fuel Trim (SHRTFT1 and 2): If the oxygen sensors are warmed up and the PCM determines that the engine can operate near stoichiometric air/fuel ratio (14.7 to 1 for gasoline), the PCM goes into closed loop fuel control mode. Since a common oxygen sensor can only indicate rich or lean, the fuel control strategy must constantly adjust the desired air/fuel ratio rich and lean to get the oxygen sensor to 'switch' around the stoichiometric point. If the time between switches are the same, then the system is actually operating at stoichiometry. The desired air/fuel control parameter is called short term fuel trim where stoichiometry is represented by 0%. Richer (more fuel) is represented by a positive number and leaner (less fuel) is represented by a negative number. Normal operating range for short term fuel trim is +/- 25%. Some calibrations will have time between switches and short term fuel trim excursions that are not equal. These unequal excursions are used to run the system slightly lean or rich of stoichiometry. This practice is referred to as using 'bias'. For example, the fuel system can be biased slightly rich during closed loop fuel to help reduce NOx. Values for SHRTFT1 and 2 may change a great deal on a scan tool when the engine is operated at different rpm and load points. This is because SHRTFT1 and 2 will react to fuel delivery variability that can change as a function of engine rpm and load. Short term fuel trim values are not retained after the engine is turned off.
    Shorty or Shortie or Short-Tube Header: A header whose collector is above the oil pan and inside the frame rails. See Header. Compare Long-Tube Header.
    SI: 1) Sequential Injection; 2) System International d'Unites (the modern international version of the metric system).
    Side Gapping: A modification of a standard spark plug so that the ground electrode approaches the side of the center electrode, instead of covering the end. The concept is that the spark will then propagate the flame front more rapidly & evenly through the combustion chamber, increasing power & economy. But the spark is concentrated to smaller areas on both electrodes, so it erodes both more rapidly, and is more susceptible to fouling. Its benefits are also questionable.
    Sidepipe: An exhaust tailpipe that runs along the side of the body under the door & exits forward of the rear tire. They are more common on grand touring coupes or roadsters, but are also popular for off-road trucks. A well-known brand was Lake, which was offered as OE on some Corvettes.
    Signal: A fluctuating electric quantity, such as voltage or current, whose variations represent information.
    SIG RTN: Signal Return.
    Signal Return (SIG RTN): A dedicated sensor ground circuit that is common to two or more sensors.
    SIL: Shift Indicator Lamp.
    Silicon: A black nonmetallic element; the most common in the Earth's crust, as a compound with Oxygen (Silicon Dioxide=Sand=Glass). It is used in semiconductors and in steel alloys, among many other applications.
    Silicone: A durable colorless polymer used in brake fluid, grease, and (for a short time) in prosthetics - particularly breast implants. Silicone grease does not dissolve in water or gasoline, and so is often used in vehicles, but it can block fuel injectors. Its grease can be formulated with a high dielectric, and is often referred to as "dielectric grease". Another forumlation ("electrical grease") is thinner and doesn't interfere with electrical contacts.
    Single-Function Reservoir[/URL] (SFR): A fuel reservoir used on '84-89 single-tank Ford trucks which may contain a filter.
    Sipe: 1) the small veins in the tread of a tire, designed to allow water to flow away from the larger tread blocks; 2) to modify the tread surface of a tire to improve its performance in specific terrain.
    SJB: Smart Junction Box.
    Skinny Pedal: (slang) accelerator; a reference to using engine power rather than skill or good sense.
    Slave Cylinder: The output device for a manual (pedal) hydraulic system. The term applies to drum brake wheel cylinders, hydraulic calipers, & clutch slave cylinders. See Master Cylinder.
    Slider: 1) A sliding window; 2) A rock slider.
    Slip Yoke: A telescoping connection between a splined shaft (usually the output shaft of a transmission or transfer case) and a U-joint in a driveshaft. Most fullsize Ford trucks use a slip yoke at the forward end of the rear driveshaft, except those with the BW 1342 t-case.
    Slip Yoke Elimination (SYE): a popular modification to a transfer case from slip-yoke to fixed-yoke. It prevents a short driveshaft on a long-travel suspension from falling out of the t-case.
    Slotted Screw: A style of screw head using a simple, straight, central groove designed to be driven by a correspondingly simple, straight-edged tool. AKA Flathead. See Screw. Contrast Phillips, Torx.
    Slotted Rotor: A disk brake rotor which has had spiral slots machined into its surface. Historically, this was done to improve braking performance due to poor friction materials which contained adhesives & other contaminants that produce gas when heated (causing the pads to 'float' away from the rotor like a hovercraft), and which also produce varnish on the friction surfaces. The slots not only allow this gas to escape, but also clean the pads. Modern pads do not suffer from these problems, so modern slots are purely cosmetic. However, removing metal from the disk's surface causes the pads & rotors to wear faster, and causes heat to build up to higher temperatures; both of which reduce braking effectiveness. See Cross-drilled Rotor, Wilwood FAQ[/URL].
    Slushbox: (slang) An automatic transmission. Contrast Grindbox.
    Smallblock: An engine family of varying displacements that share some parts & characteristics, most of which have lower displacement than most of those in another family of engines from the same manufacturer. Contrast Short Block, Long Block, Bigblock.
    Smart Junction Box: A fuse panel which includes certain functions of the GEM, LCM, DDM, or RAP.
    SME: Society of Manufacturing Engineers.
    Smog: 1) Smoke & fog; 2) (slang) vehicle emissions
    Smogged: (slang) Tested for emissions
    Smog Pump: (slang) Secondary Air pump
    Smoke Test: 1) The common method to find a leak in the evaporative system, using a special machine that generates visible (but non-toxic/nonflammable) smoke; 2) (slang) applying power to a circuit with a known but hidden fault, causing the fault to get hot enough to put off smoke, or at least become more apparent in some way, usually resulting in more damage.
    Snap Ring: A hardened spring steel ring with a gap and an eye on each end for a tool to grip & stretch the ring for installation/removal. Internal snap rings have eyes inside, and fit into an interior groove; externals have the eyes outside, and fit into an external groove.
    Snatch: A recovery technique that uses the momentum of the fast-moving extraction vehicle to overcome the inertia and other forces acting on the stuck vehicle. It is typically the most-dangerous & most-destructive technique.
    Snatch Strap: An elastic recovery strap which reduces the impact on the vehicles and converts momentum to force more smoothly (and more safely).
    Sniffer: (slang) An electronic device used to detect chemicals by sampling air; most often, refrigerant or exhaust gas.
    SOA: Spring-over axle; a method of lifting a vehicle originally built with the leaf springs passing under the axle tube. Applies mainly to Jeep & Dodge.
    SODD: Special Order Design Division
    Sol V: Solenoid valve; a valve (usually to control vacuum) operated by an integral solenoid, such as the TAB, TAD, EVR, CANP, IAC, & fuel injectors.
    Solenoid: A device consisting of an electrical coil which, when energized, produces a magnetic field in a plunger which is pulled to a central position. A solenoid may be used as an actuator in a valve or switch. A solenoid-operated switch is called relay. Few Fords before 1990 used astarter with a solenoid[/URL], but even after that, a starter relay was often still used. Most other brands of '75-95 US vehicles use only a starter solenoid with no relay, which results in most parts suppliers calling Ford-type relays 'solenoids'.
    Solid Axle: A suspension unit (typically a driving axle) which rigidly connects the 2 wheels, most often by a tube containing a differential and axleshafts. Front (steering) solid axles also include steering knuckles & universal joints of some type. Contrast IFS/IRS.
    Solid Axle Swap (SAS): The process of retrofitting a solid axle to a vehicle originally built with an independent axle; most commonly, the front.
    Spanner: A style of wrench that grips the face of the fastener (usually a large, thin nut), as opposed to the sides. Common applications include antenna nuts & wheel bearing adjusting nuts on 4WD vehicles.
    Spark Output (SPOUT): A shorting plug, connector, signal, or circuit which transmits the desired spark timing information from the PCM to the ICM.
    Spark Plug: A gasoline engine part designed to withstand high temperature & voltage (using a ceramic insulator) and produce a spark inside the combustion chamber to ignite the fuel/air mixture. See Gap, Indexing, Side Gapping.
    Speed: The magnitude of velocity (regardless of direction); distance divided by time.
    Speed Shift: Shifting a manual transmission without using the clutch by working the throttle to match the engine speed to the transmission. Commonly used in drag racing & heavy trucks, but also when the clutch system has failed in some way. Contrast Double Clutch.
    Spider Gears: (slang) The smallest gears within a normal open differential[/URL] on the pinion shaft, technically called pinion gears. They mesh with the side gears and are responsible for the differential action[/URL].
    Spool or Full Spool: A single solid piece of metal which connects an axle's ring gear to the axleshafts, providing no differentiation. Contrast Differential, Locker. Compare Lincoln-Locker.
    SPOUT: Spark Output.
    Spur Gear: A common & inexpensive gear design using straight teeth on the gear's circumference, and parallel shafts. It produces wear, noise, & irregular output speed. Contrast Helical, Bevel, Herringbone, Hypoid, Worm.
    Squeak: A high brief noise, like new tennis shoes on a clean floor.
    Squeal: A high continuous noise, like a slipping drivebelt.
    SRE: Spherical Rod End; a swivelling connection used mainly in steering & suspension systems. It contains no rubber, and so produces much more precise movement, at the expense of transmitting more NVH. See Heim.
    SS: 1) Shift Solenoid; 2) Super Sport; a high-performance vehicle, usually a V8 coupe (muscle car).
    ST: Scan Tool.
    STA: See "S" (definition 2).
    Stake: A procedure to prevent a metal part from sliding, turning, or moving by bending a small section of it so that it interferes with other parts.
    Standard Corporate Protocol: A communication language used by most automotive manufacturers for exchanging bi-directional messages (signals) between stand-alone modules and devices. Two or more signals (multiplexed) can be sent over one circuit. Included in these messages is diagnostic data that is output over the BUS+ and BUS - lines to the data link connector (DLC). This information is accessible with a scan tool.
    Standing Wave Ratio (SWR): A measure of the efficiency of a radio transmitter (usually a CB) & its antenna system. The ideal value is 1, meaning all of the energy leaving the radio's output is radiated from the antenna. Deviations from this can be caused by poor connections, coiled antenna cables, or improperly tuned antennae (wrong effective length for the average frequency). It is not related to Ground Plane, although both affect transmitting range. SWR does not affect reception.
    Static: Unmoving/stagnant/still. Contrast Dynamic.
    Step Bar: A lightweight beam below the rocker panel designed to carry the weight of a few people as they enter/exit the vehicle. Contrast Rock Slider; Nerf Bar; Exo-Cage.
    Sterling: A medium truck manufacturer owned by Ford.
    Sterling Cycle: A thermodynamic cycle used for low-torque low-maintenance applications, such as remote agricutural water pumps. The cycle is among the most efficient yet known, and can operate on virtually any fuel that creates heat. It was experimentally adapted for vehicle use in postal vans in the early 90s.
    Straight Pipe: An exhaust system with no muffler.
    Stroke: The axial distance that a piston travels within its bore; it is exactly 2x the crankshaft connecting rod journal offset from the crankshaft centerline. See also: Bore.
    Stroked: Modified (either by grinding the journals, or by installing a different crankshaft) to change (usually INcrease) the stroke.
    Stroker: An engine which has been stroked (and often bored).
    Strut: Any rigid structural member, usually within the suspension system. See also MacPherson Strut.
    Stupid Tax: (slang) the cost of vehicle repairs, usually those due to exuberant or reckless driving.
    Subframe: a removeable frame substantially heavier than the rest of the vehicle structure, but substantially smaller than the complete vehicle. It is commonly used to support the engine & front suspension in FWD monocoque & unibody vehicles, and sometimes for the rear suspension. Contrast Ladder Frame.
    Sublet: Repairs performed at a different shop than the one the owner left the vehicle in, such as a transmission rebuilder or a painter. Generally, the vehicle owner isn't aware of sublet jobs because the primary shop handles the transportation & warranty, and integrates the cost into its own bill. Contrast In-House.
    SuperCharger or SuperCharged (SC): A forced-induction system, or its primary component: a rotating mechanism driven mechanically by engine power to provide pressurized air to the intake manifold. Contrast Turbocharger, Ram Air, Naturally Aspirated.
    SULEV: Super Ultra Low Emission Vehicle.
    Suspension Lift: The modification of a vehicle's ride height by increasing the vertical distance from the frame (or unibody) to the hubs. It usually results in increased suspension travel, body sway, and approach/breakover/departure angles. It does not affect ground clearance. See Lift. Contrast Body Lift, Tire Lift.
    SUT: Sport-Utility Truck. A class of vehicles that generally includes 4-door wagon-body open-bed light trucks, & minivans designed to look like 4-door open-bed light trucks.
    SUV: Sport-Utility Vehicle. A class of vehicles that generally includes wagon-body light trucks, & minvans with slightly increased ground clearance and short wheelbase. Some are available with 4WD or AWD.
    SuvaŽ: The DuPont name for R-134a. See Refrigerant.
    SV CBV: Solenoid Valve Carborator Bowl Vent (carburetor/vacuum)
    SVO or SVT: Ford's high-performance division, originally called Special Vehicle Operations, but changed to Special Vehicle Team.
    SWAG: (slang) Slightly wild-ass guess.
    Swage: 1) A connection (usually a soft hose to a rigid nipple) secured by compressing a solid collar past a lip or barb using dies or rollers. Many power steering & A/C hoses are die swaged. 2) The tool used in this process.
    Switch: A device for making, breaking, or changing the connections in an electrical circuit.
    SWR: Standing Wave Ratio.
    System: A group of interacting mechanical &/or electrical components serving a common purpose.

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    T: 1) combustion code for Turbine; 2) Tan wire or vacuum line.
    T-case: Transfer Case
    T'stat: Thermostat
    TA: Traction Assist. A software addition to ABS which reduces wheel slippage during acceleration.
    TAB: Thermactor Air Bypass
    TACH: Tachometer.
    Tachometer (TACH): 1) a device which displays an engine's speed in RPM, most often electronic, but sometimes cable-driven; 2) a circuit that provides input for an electronic tachometer display.
    Tacoed: (slang) Bent in half, like a taco shell.
    TAD: 1) Thermactor Air Diverter; 2) Traction-Aiding Device - see Differential.
    Take-Off: 1) a category of part that is not 'new' in the sense that it has been installed on a vehicle, but was removed (usually for an upgrade) before any significant wear or aging occurred; 2) the ability of a vehicle to begin moving briskly.
    Take-Out (T/O): a branch of a wiring harness to one or a few connectors.
    Tamper-Torx: A variation of the standard Torx system requiring a tool with a central hole to fit over a central shaft within the fastener's recessed head. In some cases, the shaft may be broken out with a common drift to allow the use of a standard Torx driver.
    Tap: 1) A tool for cutting internal threads into a drilled hole. Contrast Die, Thread Chaser; 2) A light repetitive noise, like a pencil on a desk.
    Tappet: See Lifter.
    TB: Throttle Body.
    TBI: Throttle Body Injection. AKA CPI
    TBW: Throttle-By-Wire
    TC: 1) Traction Control. Combines anti-lock braking and axle torque reduction (through electronic throttle control) to control wheel slippage; 2) Torque Converter; 3) Transfer Case; 4) Total Crash (slang/police).
    TCC: Torque Convertor Clutch.
    TCIL: Transmission Control Indicator Lamp.
    TCS: Transmission Control Switch.
    TDC: Top Dead Center; the point at which a given crankshaft lobe (usually #1) is perfectly aligned with its connecting rod, and the piston is at its maximum distance from the crankshaft.
    Tear Tag: The two—piece adhesive label attached to the PCM to identify its calibration.
    TeflonŽ: The original DuPont name for PTFE (polytetrafluoroethylene).
    Temp: 1) Temperature; 2) Temporary.
    Terminal: A point of attachment for any electrical conductor, generally within a connector. Some terminals are left unconnected for testing, or for optional circuits which are not installed. Any single circuit may have 2 or more terminals. Terminals are typically clad copper stamped into a shape that promotes good mechanical contact on one end, and has a crimpable or solderable area for wires on the other. The cladding may be zinc, solder, gold, or several other metals & alloys. Common terminal shapes include ring, spade, flat, tube, bullet, pin, alligator, blade, & banana.
    Test: A procedure whereby the performance of a product, system, part, or person is measured under various conditions.
    TFI-IV: Thick-Film Integrated (generation 4) ignition control module used with EEC-IV, and also called DI (Distributor Ignition).
    TFT: Transmission Fluid Temperature. AKA TOT.
    Therm: 1) Thermometer; 2) Thermostat; 3) Thermactor; 4) Thermistor.
    Thermactor Air Bypass (TAB): A signal, circuit,solenoid valve[/URL], vacuum line, or air valve[/URL] which directs the output of the secondary air pump either to the TAD or to an exhaust muffler[/URL].
    Thermactor Air Diverter (TAD): A signal, circuit, solenoid valve[/URL], vacuum line, or air valve[/URL] which directs the flow of secondary air either to the exhaust manifolds (upstream[/URL]) or to the catalytic converter (downstream), through a check[/URL]valve[/URL] in either case.
    Thermistor: A temperature dependent resistor, like that used in CHT and ECT sensors.
    Thermostat: An automatic temperature-triggered (usually wax-filled) valve that opens when the engine coolant exceeds a design temperature (usually 190°F) to allow the coolant to begin circulating through the radiator. It generally does not affect the heater circuit, and only affects the engine's operating temperature in certain failure modes. It also acts as a restriction, causing slightly higher pressure inside the engine which reduces the tendency of the coolant to boil. This effect has caused confusion about removing a t'stat, leading to the myth that fast-moving coolant doesn't transfer heat as well.
    Third Member (3rd Member): a section of a drive axle housing which contains the pinion & ring (crown) gears, and can be removed from the axle tube assembly. It also contains the differential, if equipped. AKA Chunk, Center Section, Hog Head.
    Thread Chaser: any tool designed to clean a specific thread pitch, diameter, & direction, similar to a tap or die. Some are adjustable; some expand or compress to reach past damaged threads and start on good threads (back-tap, split die). Contrast Thread File.
    Thread File: a tool designed to clean external threads. A single-cut file will clean any thread pitch or diameter in either direction; a multi-cut file will clean a specific pitch of any diameter in either direction.
    Three Way + Oxidation Catalytic Convertor (TWC+OC): A catalytic convertor system that has both Three Way Catalyst (TWC) and Oxidation Catalyst (OC). Usually secondary air is introduced between the two catalysts.
    Three Way Catalytic Convertor (TWC): A catalytic convertor system that reduces levels of HC, CO, and NOx.
    Throttle: A valve for regulating the supply of a fluid, usually air or an air/fuel mix, to an engine.
    Throttle Body (TB): The device containing the throttle.
    Throttle Body Injection (TBI): A fuel-delivery system in which 1 or 2 injectors are located in the throttle body to distribute fuel through the intake manifold to the cylinders. AKA Central Fuel Injection. Contrast Multiport Fuel Injection.
    Throttle Position (TP orTPS[/URL]): A sensor, signal, or circuit which indicates the position of the throttle plate. Early types required adjustment; later PCM programming eliminates the need for adjustment because the PCM simply adapts tothe sensor's output[/URL] (within a relatively wide range).
    Tie Rod: Any rod, bar, tube, or shaft comprising the steering linkage; especially those with a ball stud end.
    Tie Rod End (TRE): the tapered stud, swivel ball, & socket with a threaded shaft for connection & adjustment used in most steering linkages. Other than the threaded shaft, it is identical to a ball joint, but built lighter.
    Tie Rod Over (TRO): The modification of the steering knuckles to allow the tie rod studs to be inserted from the top, providing more approach angle or ground clearance, and possibly improving steering linkage geometry. AKA High Steer.
    Tier 0: California regulations effective prior to 1993 model year, and Federal regulations prior to 1994 model year.
    Tier 1: California and Federal regulations effective beginning in 1993 model year and Federal regulations beginning in 1994 model year.
    Tighten it until it loosens: A joke among mechanics about overtightening fasteners to the point that the threads strip.
    Timing: Relationship between spark plug firing and piston position usually expressed in crankshaft degrees before (BTDC) or after (ATDC) top dead center of the compression stroke.
    Tire Lift: The modification of a vehicle's ride height by installing larger tires. For every 2" of tire increase, the vehicle rises 1", increasing ground clearance and approach/breakover/departure angles, but usually reducing suspension travel (unless the body is cut out or lifted). Larger tires also affect alignment angles and wheel bearing life. See Lift. Contrast Suspension Lift, Body Lift.
    TK: Throttle Kicker (carburetor/vacuum)
    TLEV: Transitional Low Emission Vehicle.
    Tone Ring[/URL]: A toothed or notched iron or steel disk, which is attached to a rotating part. AKA exciter Ring, Sensor, Sensor Ring.
    Torque: The force of rotation, commonly measured in lb-ft (for rotating parts), ft-lb (for non-moving parts, like fasteners), or Nm.
    Torque-Biasing Differential: A differential whose internal mechanisms vary the division of the input torque (engine) proportionally to the outputs' resitance
    (traction). Contrast Open Differential, Limited-Slip Differential, Locker.
    Torque Convertor: A device which by its design multiplies the torque in a fluid coupling between an engine and transmission/transaxle.
    Torque Convertor Clutch (TCC): A solenoid valve, signal, or circuit which controls the application and release of the torque convertor clutch.
    Torque Wrench: A calibrated instrument for precisely tightening fasteners, or adjusting rotating assemblies. Some have ratcheting drives.
    * Micrometer or 'click-type' wrenches use a spring on a toggle with a mechanism for adjusting the tension on the spring. When the set torque is reached, it overcomes the spring and causes the toggle to click out of place. They must always be stored at their minimum setting, and do not work for rotating assemblies.
    * Beam-type wrenches use a calibrated spring steel handle with a scale, and a free pointer that indicates how far the handle has bent.
    * Dial-type wrenches are the most precise and work on rotating assemblies. But they are the easiest to overstress, which typically ruins them.
    * Electronic wrenches are easy to use and are reasonably accurate, but don't work for rotating assemblies.
    Torx: A tool or fastener drive shape utilizing a 6-point star, similar to an asterisk (*). It may be standard (male driver; female fastener head) or inverse (female driver; male fastener head).
    TOT: Transmission Oil Temperature. AKA TFT.
    TP: Throttle Position.
    TR: Digital Transmission Range sensor.
    Track Bar: 1) See Panhard Bar; 2) See Drag Link; 3) See Traction Bars.
    TracLok: Traction Lok
    Traction Bars: Simple bars added to a rear leaf spring solid axle suspension to limit axle wrap, improving traction.
    Traction Control (TC): Combines anti-lock braking and axle torque reduction to control wheel slippage.
    Traction Lok: A particular model of LSD manufactured by Eaton & used extensively by Ford as OE in many cars & light trucks.
    Trailer Queen: A disparaging term for a vehicle which must be trailered to go any distance.
    Transaxle: A device integrating the functions of a transmission and axle drive gears (differential) assembled in one case. Most commonly used in FWD vehicles, but also in modern Corvettes at the rear. Compare Transmission, Axle
    Transducer: A device that receives energy from one medium and transfers it to another. For example, thermal energy is converted to an electrical signal through a thermocouple; light energy is converted to electricity through a solar cell.
    Transfer Case: A driveline component that divides torque to the front & rear axles, and may also change the speed.
    Transmission: A device which selectively increases or decreases the ratio of relative rotation between its input and output shafts. Compare Transaxle. Current (2008) Ford transmission naming convention is as follows:
    * The first character, a number, is the number of forward gears.
    * The second character, either the letter 'F' or 'R' represents front (transaxle) or rear (transmission) wheel drive.
    * The next characters, a grouping of numbers, represents 1/10 the design torque capacity of the transmission/transaxle.
    * The last character, if used, is one of the following:
    * * 'E' for electronic shift
    * * 'N' for non—synchronous shift
    * * 'S' for synchronous shift
    * * 'W' for wide ratio
    Transmission Control Indicator Lamp (TCIL): Indicates that the TCS has been activated. Typically mounted to the end of the shift lever of an automatic transmission, and incorporated with the TCS. AKA OCIL.
    Transmission Control Switch (TCS): Modifies the operation of electronically controlled transmissions. Typically mounted to the end of the shift lever of an automatic transmission, and incorporated with the TCIL. AKA OCS.
    Transmission Fluid Temperature (TFT): A sensor, signal, or circuit which indicates the temperature of transmission fluid.
    Transmission Range (TR): A sensor, signal, or circuit which indicates the range in which the transmission is operating.
    Triple Square: A style of fastener & matching tool with 12 90° points. Contrast Double Hex.
    Truck: A cargo or utility vehicle, generally built on a full ladder-frame with a cab separate from its cargo area, a front engine, RWD, and few luxuries. Compare Light Truck, Semi-Truck, Van. Contrast Convertible, Coupe, Pickup, Roadster, Sedan, Wagon-body.
    True Duals: See Dual Exhaust.
    True-Trac: A particular model of Torque-Biasing Differential originally designed by TracTech, which is now owned by Eaton.
    TRW: A parts company, primarily chassis components.
    Turbine Shaft Speed (TSS): A sensor, signal, or circuit which indicates the rotational speed of the transmission turbine shaft.
    Turbocharger: A forced-induction system, or its primary component: a rotating mechanism driven by exhaust gas flow to provide pressurized air to the intake manifold. Contrast Supercharger, Ram Air, Naturally Aspirated.
    TSB[/URL]: Technical Service Bulletin. A document published by a motor vehicle manufacturer containing
    technical information intended to be used by trained technicians to assist in identifying & repairing a specific concern on a specific group of vehicles. It generally contains criteria for identifying affected vehicles, specific procedures for the repair, a list of required &/or recommended parts, and the authorized labor time for which a flat-rate dealership technician will be paid.
    TSS: Turbine Shaft Speed.
    TTB[/URL]:Twin Traction Beam[/URL].
    TVS: Throttle Valve Solenoid (aka SolePot, Dashpot) (carburetor/vacuum)
    TVV: Thermal Vacuum Valve (carburetor/vacuum)
    TWC: Three Way Catalytic Convertor.
    TWC+OC: Three Way + Oxidation Catalytic Convertor.
    Twin Traction Beam[/URL](TTB[/URL]): A copyrighted name for the Dana 28IFS, 35IFS, 44IFS, & 50IFS axles used exclusively in Ford 4WD/AWD light trucks from the early 80s to the late 90s. Its design is the basis for many long-travel IFS axles used on off-road race trucks.
    Two Barrel or Two Veturi (2V): A design of carburetor using 2 throttle bores.
    Two-Cycle: (slang) See Two-Stroke Cycle.
    Two-Stroke: (slang) See Two-Stroke Cycle.
    Two-Stroke Cycle: An engine operating system that involve 2 strokes of each piston to complete one combustion cycle (a version of the Otto combustion cycle). On the up stroke, the piston is forced up by the crankshaft. Any remaining exhaust near the piston is pushed out the exhaust port as the piston passes it. The fresh air-fuel-oil mix near the intake valve becomes trapped in the chamber & is compressed. Within the crankcase, the rising piston's rear face creates a vacuum which draws in more air & fuel/oil mix through the reed valve behind the carburetor. Near the top of that stroke, the compressed fuel in the chamber is ignited either by a glow plug or a spark plug. On the down stroke, the burning fuel in the chamber forces the piston down, transferring power to the crankshaft. It also pressurizes the crankcase slightly. As the piston passes the exhaust port, pressure in the cylinder expels the burned fuel. Eventually, the pressure drops below the threshhod for the reed valve in the head, allowing the pressurized crankcase fuel-air-oil mix into the chamber. The cycle then repeats. Because only 1 stroke consumes power for each 1 that produces power, 2-stroke engines are inherently more powerful by weight & more thermodynamically efficient than 4-strokes. But they require more maintenance & produce more emissions because their fuel (which flows continuously thru the crankcase) must carry lubricating oil (which passes thru the combustion chamber & out the exhaust).
    Two Valve (2V): Two valves, one intake and one exhaust, per cylinder.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    Reserved: for future expansion.


    Discrete: A circuit (wire) running exclusively between 2 components with a single function. For example: the TCIL circuit is a discrete power ground (very low-current) between the EEC/PCM and the TCS assembly. But the BOO output is not discrete because it has many connections, and it may be powered by the BOO, or it may be a ground for the cruise servo, or it may be a logical input for the EEC/PCM.

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    Default Re: Terms & Abbreviations

    To find a term or abbreviation (on this or almost any web page), hit CTRL+F and type the search term, then press ENTER as many times as needed.

    U-Bolt: 1) A U-shaped bolt, both of whose ends are threaded. It is commonly used for U-joints, and for holding axle tubes to leaf springs. 2) (slang) a U-turn.
    U-Joint: Universal Joint, usually Cardan style.
    U-Nut: A stamped, formed, & hardened sheet metal nut that is U-shaped to slip over the edge of thin material. It provides a stronger threading surface for a bolt or screw than the material onto which it is installed. Unlike a J-nut, the male fastener passes through a hole in each layer of the U-nut.
    ULEV: Ultra Low Emission Vehicle.
    Unibody or Unit Body: A medium-weight style of vehicle construction in which a stressed cosmetic skin covers a lightweight framework for the vehicle's general shape. The skin adds no real strength to the structure, and there is very little (if any) heavier structure, to which the suspension & drivetrain are attached. Contrast Monocoque, Ladder Frame.
    Unit Bearing: a modern wheel bearing system using 2 sealed ball-bearing assemblies pressed into either a removeable carrier or a steering knuckle. A splined tubular hub is pressed through the bearings.
    Universal Joint: A mechanism that allows a rotating shaft to flex in any direction without significantly interfering with its rotation. Common types include cross (Cardan, Hooke's, Hardy-Spicer), rag (Jured, membrane), cable, dog-bone, and CV.
    V: 1) Volt; 2) Vacuum; 3) Valve; 4) Vapor; 5) Violet (purple) wire or vacuum line; 6) Vehicle; 7) Variable.
    Vacuum: Air pressure below ambient,typically created by a throttle. Gasoline engines operate with a vacuum in the intake manifold to control power output. Diesels cannot operate with manifold vacuum, and do not have throttles.
    Vacuum Booster[/URL]: A power-assist mechanism for vehicle brakes which uses vacuum pressure to amplify the force applied to the brake master cylinder. Contrast HydroBoost[/URL].
    Vacuum-Fluorescent Display (VFD): An electronic display which uses fluorescent gases inside a glass vacuum chamber to produce luminescent characters & symbols. VFDs are relatively heavy, complex, fragile, & inefficient compared to other display types, but have the advantages of high contrast & producing their own light. They are typically bright green, and are commonly used on radios & all-digital instrument clusters. Contrast LED Display, LCD.
    Vacuum Manifold: a manifold pipe used to distribute vacuum.
    Vacuum Reservoir: A chamber (usually molded plastic[/URL] or a steel[/URL] can[/URL]) to provide vacuum for actuators during conditions when engine-generated vacuum may not be available.
    Vacuum Tee or T: a manifold pipe used to distribute vacuum, resembling the capital letter T.
    Vacuum Tree[/URL]: A vacuum manifold with several nipples radiating from a central fitting, resembling branches radiating from the trunk of a tree.
    Valve: A device by which the flow of liquid, gas, vacuum, or loose material in bulk may be started, stopped or regulated by a movable part that opens, shuts or partially obstructs one or more ports or passageways. A "Valve" is also the moveable part of such a device.
    Valve Clatter: See Knock.
    Van: A fullsize or larger truck whose cab significantly overhangs its engine bay, resulting in the front wheelwells encroaching into the front passengers' footwells. Most vans are built on ladder frames. Contrast Convertible, Coupe, Pickup, Roadster, Sedan, Truck, Wagon-body.
    Vapor: A form of a substance which is normally liquid, but has been heated enough to become a gas, or has been atomized finely enough to be suspended within a gas (usually air), such as gasoline going thru a fuel injector or evaporating within the tank, or fog (water vapor in air).
    Vapor Lock: a condition in which gasoline in a suction line (upstream of a mechanical reciprocating pump) is subjected to higher-than-normal temperature (headers) and lower-than-normal pressure (low level in the tank), causing it to vaporize within the line. Because of the reciprocating nature of the pump (operated by a cam & lever) and the elastic nature of vapors (same reason air in a brake line causes problems), the pump can't move the fuel, and the engine stalls. The solutions are to raise the pressure by raising the fuel level in the tank, &/or shield the line from the heat (or reroute it). This phenomenon DOES NOT AFFECT EFI systems because they maintain very high fuel pressure, which prevents boiling, even when the fuel lines are exposed to high temps.
    Vapor Management Valve (VMV): A valve that controls the amount of fuel tank vapor burned in the engine.
    Variable Load Control Module (VLCM): A module that provides variable control of various EEC components.
    Variable Reluctance: A process of passing a varying magnetic field through wire windings and inducing a voltage.
    V-CBV: Vapor Canister Bowl Vent (carburetor/vacuum)
    VCT: Variable Camshaft Timing. A system which adjusts the mechanical timing between the crankshaft & the camshaft(s). AKA VVT.
    VCV: Vacuum Control Valve (carburetor/vacuum)
    VCKV: Vacuum Check Valve (carburetor/vacuum)
    VDF: Visctronic Drive Fan. An electrically-assisted viscous fan coupling.
    VDV: Vacuum Delay Valve; Vacuum Diverter Valve (carburetor/vacuum)
    VE: Volumetric Efficiency.
    Vehicle Emissions Control Information (VECI) Label: a factory sticker showing vehicle-specific information, codes, & diagrams describing the factory-installed emissions systems, and tune-up information.
    Vehicle Certification (VC) Label: a factory label typically applied in the driver's door jamb with critical build information, including month/year of manufacture, country of origin, VIN, and sometimes tire & optional equipment data. AKA Safety Certification Label, Door Sticker.
    Vehicle Power (VPWR): A switched circuit that provides power to the EEC system. Compare "Battery Positive Voltage (B+)."
    Vehicle Speed Control (VSC): Cruise control system. Early types use a vacuum servo[/URL] & speed sensor on the speedometer cable[/URL]. Later types use an electronic servo[/URL] & speed sensor in the transmission or differential.
    Vehicle Speed/Engine RPM Limiter: A strategy to prevent damage to the powertrain. The powertrain control module (PCM) will disable some or all of the fuel injectors whenever an engine rpm or vehicle overspeed condition is detected. The vehicle will exhibit a rough running engine condition, and the PCM will store a Continuous Memory DTC P1270. Once the driver reduces the excessive speed, the engine will return to the normal operating mode. No repair is required. However, the technician should clear the PCM and inform the customer of the reason for the DTC. Excessive wheel slippage may be caused by sand, gravel, rain, mud, snow, ice, etc. or excessive and sudden increase in rpm while in NEUTRAL or while driving.
    Vehicle Speed Sensor[/URL] or Signal (VSS): A sensor, signal, or circuit which provides vehicle speed information. Until ~1989, this was used primarily by the VSC, and from '89~92 it was also used for E4OD control on F-series trucks. It may also be used for entertainment systems for speed-relative volume control, navigation systems, theft systems, or thermometer corrections. It is typically installed in the speedometer cable, the transmission tailhousing, or the transfer case rear output housing. All EFIs use VSS for return-to-idle control of the IAC, especially with manual transmissions. Contrast ABS(2).
    VFD: Vacuum-Fluorescent Display.
    Vibration: Any continuous sensation that a vehicle occupant finds objectionable.
    VIN[/URL]: Vehicle Identification Number. A code uniquely identifying a vehicle, standardized to 17-digits in 1981. The encoded information typically includes country of origin, manufacturer, GVWR/brake capacity/restraint type, body style, body size, chassis type, engine size, MY, production plant, & serial number. There is also a verification code to prevent random VINs from being generated.
    VIN Sticker: SeeVehicle Certification Label[/URL].
    Viscosity[/URL]: A measure of the ability of a fluid (usually a liquid) to flow. AKA Weight in oils. In the format "xxWxx", the first number indicates the actual viscosity of the oil at room temperature (~70°F); the number following "W" indicates the effective viscosity at operating temperature (~220°F) due to the additive package blended with the base oil.
    VLCM: Variable Load Control Module.
    VMV: Vapor Management Valve.
    Volt (V): the standard measure of electromotive potential or force, analogous to pressure in water.
    Volumetric Efficiency (VE): A comparison of an engine's actual airflow to its theoretical flow, based on displacement & RPM. The actual flow will always be less with natural aspiration, due to turbulence, temperature changes, and the throttle effect.
    VOM: Volt-Ohm Meter. Non-specific, so generally used for analog (needle) meters to differentiate from DVOMs & DMMs (DIGITAL meters).
    VPWR: Vehicle Power.
    VRDV: Vacuum Retard Delay Valve for the distributor (carburetor/vacuum)
    VREF: Reference Voltage, generally ~5VDC supplied from the PCM to certain transistorized sensors.
    VSC: Vehicle Speed Control.
    W: White wire or vacuum line.
    WAC: Wide Open Throttle A/C Cut-off.
    WAG: (slang) Wild-ass guess.
    Wagon-body: A vehicle whose cargo area is integral to its cabin structure, most commonly: 4-door station wagons, 2- & 4-door SUVs, vans, & minivans. Box vans are not included since the box is added later, but panel vans are. Contrast Convertible, Coupe, Pickup, Roadster, Sedan, Truck, Van.
    Wankel: a unique engine design using a bulging triangular piston that rotoates & wobbles within a figure-8 chamber. It is remarkably efficient (a version of the Otto combustion cycle) because it effectively operates 3 simultaneous 2-stroke cycles, but doesn't require oil to be mixed into the fuel. A Wankel rotary engine may incorporate several such pistons stacked in a very small block. Its main drawback is the high wear that the seals on the piston are subject to. It has only been used in 1 production vehicle: the Mazda RX (Rotary Experiment) models, but it is popular for miniature airplanes because of its similarity in appearance to a radial engine.
    Warm Up Oxidation Catalytic Convertor (WU-OC): A catalytic convertor system designed to lower HC and CO emissions during engine warm up. Usually located in or near the exhaust manifold.
    Warm Up Three-Way Catalytic Convertor (WU-TWC): A catalytic convertor system designed to lower HC, CO, and NOx emissions during engine warm up. Usually located in or near the exhaust manifold.
    Wastegate: A valve that allows unneeded pressure from a turbocharger to bypass the intake system.
    Wastegate Control: A device that opens a turbocharger's wastegate in case of overboost.
    Watts Link: A method of laterally locating an axle, consisting of 2 long bars attached either to the frame or axle at their far ends, and a 3rd bar between them with a single point of attachement. The middle section of the bar is nearly vertical at normal ride height, allowing the axle to roll (sway) or to move straight up & down, but not laterally. Contrast Panhard Bar, Mumford Link.
    Weekend Warrior (WW): An off-road-capable vehicle that is still technically street-legal, but isn't comfortable or reliable enough for daily use or work. It is only used for play, and must usually be towed to wheeling events.
    Weight: 1) See Viscosity. 2) A wheel balancing weight. 3) See GVWR and Curb Weight.
    Wheel Cylinder: A slave cylinder for a hydraulic brake system located near a wheel or hub. The term is typically used only to describe a drum brake slave cylinder, and not for a disk brake caliper's cylinder. See Master Cylinder.
    Whir or Whirr: A light steady medium noise, like a small fan.
    Whistle: A brief sharp noise, like metal scraping glass.
    Wide Open Throttle (WOT): A condition of maximum airflow through the throttle body.
    Wide Open Throttle A/C Cut-off (WAC): Turns A/C system off during wide open throttle or certain other operating conditions.
    Wing: See Fender.
    WMS: Wheel Mounting Surface; the distance between the hub flanges on an axle assembly. AKA hub-to-hub.
    Wonky: (slang) fully articulated; front suspension at the opposite limit from the rear. AKA Crossed Up, Cross-Axled.
    Worm Gears: A common gear-reduction system whose axes are perpedicular & do not intersect. The "worm" gear resembles a short section of threaded bolt, which drives a helical gear in mesh. They are commonly used for speedometer drives, winches, & one-way mechanisms since the helical gear cannot drive the worm (reverse). Contrast Helical, Bevel, Herringbone, Hypoid, Spur.
    WOT: Wide Open Throttle.
    Wristed Axle Housing (WAH): A solid axle whose tube has been cut and flanged back together so the control arms can rotate in relation to each other during articulation.
    WU-OC: Warm Up Oxidation Catalytic Convertor.
    WU-TWC: Warm Up Three-Way Catalytic Convertor.
    XL: A Ford truck trim level just above Custom (in years when Custom was offered) including VERY few options, if any. Compare Custom, XLS, XLT, XLT Sport, Nite, Lightning, Eddie Bauer.
    XLPE: Cross-Linked PolyEthylene; a plastic used for (among other things) high-temperature wire insualtion, instead of PVC.
    XLS: XL Sport. An off-road performance package offered on Broncos & 4WD F150s in the early 80s, but with very few comfort/convenience options. Compare Custom, XL, XLT, XLT Sport, Nite, Lightning, Eddie Bauer.
    XLT: A Ford truck trim level above XL including most of the available options for the given year model. Compare Custom, XL, XLS, XLT Sport, Nite, Lightning, Eddie Bauer.
    XLT Sport: A cosmetic option package above XLT for '93-96 F150s & Broncos including monochromatic paint in black, red, or white. It is effectively the same as the Lightning package without the engine/suspension modifications. Compare Custom, XL, XLS, XLT, Nite, Lightning, Eddie Bauer.
    Xmbr: Crossmember.
    Xmitter: Transmitter.
    X-Pipe: a method of interconnecting the banks of a dual exhaust system in which the tubes are bent together, cut open on their adjoining sides, and welded together to form an "X" where exhaust flow is uninterrupted, but pressure waves can cross over freely. It is often used in an attempt to make a true dual system more efficient.
    Y: Yellow wire or vacuum line.
    YMMV: Your Mileage May Vary; a common generic disclaimer used on discusion forums, whether about gas mileage or not.
    YRMV: Your Results May Vary; a common generic disclaimer used on discusion forums.
    Yoke: A 1-piece connection between a splined shaft & a U-joint in a driveshaft. One end is a splined sleeve that fits over the shaft & inside an oil seal. The other end spreads across the caps of the U-joint and attaches either by 2 U-bolts & 4 nuts, 4 bolts & 2 straps (GM & Dodge), or a cast mating cap with 4 bolts (double-cardan applications). Commonly misspelled "yolk" (the center of an egg).
    Z: fuel code for Electric
    Zerk: inventor of the grease nipple.
    ZEV: Zero Emission Vehicle.
    Zip Tube: Another name for "fresh air duct" or "air inlet duct". The hose connecting the air filter box to the throttle body.

    An acronym is an abbreviation that can be pronounced as a word, like:
    Nazi (National Sozialistische Deutsche Arbeiters Partei)
    SCUBA (Self-Contained Underwater Breathing Apparatus)
    LASER (Light Amplification by Stimulated Emission of Radiation)
    SONAR (Sound Navigation & Ranging)
    MASH (Mobile Army Surgical Hospital)
    WASP (White Anglo-Saxon Protestant)
    GIGO (Garbage-In; Garbage-Out)
    WYSIWYG (What You See Is What You Get)

    HMMWV (High-Mobility Multipurpose Wheeled Vehicle - hummvee) & STFU (Shut The F**k Up - stoofoo) are commonly used as acronyms, even though they aren't really.

    TTT (To The Top), BTT (Back To Top), FTW (For The Win), NWS (Not Work-Safe), NSFW (Not Safe For Work), TTB (Twin Traction Beam), TFI (Throttle-body Fuel Injection), AFAIK (As Far As I Know), IDK (I Don't Know), & IBTL (In Before The Lock) are just abbreviations because they can't be pronounced as words.

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