Terms & Abbreviations

[Steve83]

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.

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.
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.
4R44E: 4 speed, Rear wheel drive, 440 lb-ft, Electronic transmission, derived from the AODE.
4R55E: 4 speed, Rear wheel drive, 550 lb-ft, Electronic transmission, derived from the AODE.
4R70W: 4 speed, Rear wheel drive, 700 lb-ft, Wide ratio electronic transmission, formerly known as AODE.
4R100: 4 speed, Rear wheel drive, 1000 lb-ft, electronic transmission, formerly known as E4OD.
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.
4X2: See 2WD.
4X4: See 4WD.
4x4 Low (4x4L): Indicates the 4x4 Low range of the transfer case has been selected.
4x4L: 4x4 Low.
5R55W: 5 speed, Rear wheel drive, 550 lb-ft, Wide-ratio electronic truck transmission, derived from the 4R70W.
A: combustion code for Other
A-Arm: A suspension strut shaped like a horizontal "A", with the legs attached to the vehicle frame & the top attached by a ball joint to the steering knuckle.
A/C: Air Conditioning.
A/CL DV: Air Cleaner Diverter Valve (carburetor/vacuum)
A/CL BI MET: Air Cleaner BiMetallic valve (carburetor/vacuum)
A/D: Analog-to-Digital signal conversion.
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.
A-Pillar: The front-most body structure for supporting the roof of a vehicle. Subsequent pillars are designated "B", "C", etc.
A/T: Automatic Transmission/Transaxle.
ABS: 1. Anti-lock Brake System; 2. A sensor, signal or circuit which supplies rear axle speed data either to the RABS (or RABS-II) module, the 4WABS module, the PSOM, &/or the EEC (for electronic automatic transmission control & return-to-idle). After processing by the 4WABS module &/or the PSOM, the signal is also fed to the VSC & the Bronco overhead console (for temperature adjustment); 3. A type of plastic. Compare PVC.
Absolute Pressure: The pressure referenced to a perfect vacuum. Contrast gauge pressure, which references atmospheric pressure (~14.7psi above perfect vacuum).
ACC: Air Conditioning Clutch.
Accordion: See Crumple Zone.
ACCS: Air Conditioning Cycling Switch.
ACD: Air Conditioning Demand.
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)
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.
AFCM: Alternative Fuel Control Module.
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.
AIR BPV: Air ByPass Valve. AKA TAB (carburetor/vacuum)
Air Conditioning (A/C): A vehicular accessory system that modifies the passenger compartment air by cooling and drying the air.
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 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.
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: A term copyrighted by Chrysler Corporation. See Generator.
ALVW: Adjusted Loaded Vehicle Weight, defined by (Curb Weight + GVWR) /2.
Ambient Temperature: Temperature of the air surrounding an object.
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.
AOD: Automatic Overdrive transmission. Predecessor to AODE, 4R70W, 4R44E, 4R55E, 5R55W.
AODE: Automatic Overdrive Electronic transmission.
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: Automotive Service Excellence; an organization that establishes & maintains standards in the auto service industry, most notably by adminstering tests for technicians.
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, power steering systems, hydraulic brake boosters, manual transmissions, & transfer cases. Examples include: Type A, Type F, Mercon (I-V), MerconSP, MerconLV, FNR5, CVT, Dexron (I-V), ATF+2, ATF+3, ATF+4.
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. Contrast RWD, FWD, 4WD, 2WD.
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.
B+: Battery Positive Voltage.
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.
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.
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 "Vehicle Power (VPWR)."
BATTEMP: Battery Temperature.
BBL: Barrel (carburetor/vacuum). Compare Venturi.
BCM: Body Control Module - an electronic component that generally controls systems unrelated to the powertrain.
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 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"; two is "10"; three is "11"; nine is "1001"; fourteen is "1110".
BJB: Battery Junction Box.
Bk: Black wire or vacuum line.
Blinker Fluid: A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
Block Test: See Dissolved Gas Test.
Blower (BLR): A device designed to supply a current of air at a moderate pressure. It usually consists of an impeller assembly, a motor and a suitable case. The blower case is designed as part of the ventilation system.
BLR: Blower.
Bn: Brown wire or vacuum line.
Body Lift: 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.
Bolt: A medium- or heavy-duty machine-threaded fastener, generally with a hex head to be driven by a wrench into either a threaded hole or a nut. See Grade. Contrast Screw.
BOO: Brake On/Off.
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. Cotrast Jumper Cables.
Booster Pack: See Jumper Battery.
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.
BPA: Bypass Air; see IAC.
BPA-ISC: Bypass Air Idle Speed Control solenoid; see IAC.
BPP: Brake Pedal Position.
Br: Brown wire or vacuum line.
Brake On/Off (BOO): A 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.
Brake Pedal Position (BPP): A sensor, signal, or circuit which indicates the position of the brake pedal for use by the traction control &/or restraint systems. Compare BOO.
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.
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/without PTO (Aluminum front case); with/without speedo gear bore; fixed/slip rear output; yoke/companion flange rear output.

[Steve83]

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.

Cab: The cabin of a truck or a piece of equipment.
Cabin: The operator & passenger compartment(s) of a vehicle or piece of equipment. Except for unibody, distinguished from the chassis, cargo area, & accessory attachments.
CAC: Charge Air Cooler. See Intercooler.
CAFE: Corporate Average Fuel Economy. A set of federal requirements and regulations which stipulate fuel economy standards based on a manufacturer's entire production output.
CAI: Cold-Air Intake, often confused with open-element air filter.
Camshaft: A shaft on which phased cams are mounted or cast. The camshaft is used to regulate the opening and closing of the intake and exhaust valves.
Camshaft Position (CMP): A sensor, signal, or circuit which indicates camshaft position.
Cancer: (slang) Rust.
Canister: A device designed to hold dry material. An evaporative emission canister contains activated charcoal (carbon) which absorbs fuel vapors and holds them until they can be purged into the intake.
CANP: Canister Purge.
Canister Purge (CANP): A solenoid valve, or the signal or circuit which controls it, to purge the carbon canister. Compare VMV.
CANV: Canister Vent.
Canister Vent (CV, CANV): A solenoid valve, or the signal or circuit which controls it, to allow fresh air into the carbon canister.
Cap or Capacitor: An electrical component that stores energy in an electrical field, like static on a balloon. AKA condenser.
Captive: A separate & loose part that cannot be easily removed from the primary part, such as a captive washer on a bolt or screw.
CARB: California Air Resource Board; a government agency which sets & enforces emissions standards within California, and issues certifications of compliance to aftermarket parts.
Carbon Fiber: A fiber material formed by (essentially) burning plastic (acrylic) fibers in a deoxygenated kiln, resulting in microscopic tubes of graphite. These fibers can then be used to reinforce resins, in the same way fiberglass or Kevlar are. Carbon fiber is between fiberglass & Kevlar both in strength and price, but can be made higher in rigidity than either. In some applications, it is woven into sheets & embedded in a transparent resin, resulting in a distinctive pattern that is often imitated purely for cosmetic & marketing purposes.
Cardan joint: The most common type of universal joint consisting primarily of a right-angled cross-shaped trunnion with caps on needle bearings. AKA Hooke's joint, Hardy-Spicer joint. See also Double Cardan Joint.
Cardone: a parts company.
CARS: 1) Consumer Assistance to Recycle and Save Act (the original legislation name); 2) Car Allowance Rebate System (the name of the program); 3) Cash for Clunkers (the popular name) (C4C). A US program touted as beneficial for the environment, but actually just a continuation of the stimulus package for US automakers, which failed and ultimately cost US taxpayers about $2K per vehicle. It actually benefitted foreign automakers far more than US, and only Ford maintained its market share. Because new fuel-efficient vehicles stimulate driving, US emissions are slightly higher than they would have been without the program.
Carter Pin: slang. See Cotter Pin.
Case Ground (CSE GND): The dedicated circuit from the PCM case to chassis ground.
Castellated Nut or Castle Nut: A nut with slots cut across one face to allow a cotter pin to lock it, commonly used on suspension studs & bolts.
Catalyst: A material which facilitates or accelerates a chemical reaction without being consumed. See also Catalytic converter.
Catalytic Convertor: An in-line, exhaust system device used to reduce the level of engine exhaust emissions. AKA Thermactor.
C.B.: 1) Circuit Breaker; 2) Citizen's Band.
CCD: Computer Controlled Dwell; Charge Coupled Device (a digital image sensor).
CCRM: Constant Control Relay Module.
CCS: Coast Clutch Solenoid.
CD: 1) fuel code for Bi-Fuel, CNG/Diesel; 2) Compact Disk - an optical data storage medium, including music CDs & DVDs
CD4E: CD class vehicle, 4 speed, Electronic transmission.
CEL: Check Engine Light. See MIL.
Central Point Fuel Injection (CPI/CFI): See Throttle-Body Fuel Injection.
Centurion: A vehicle customizing company closely affiliated with Ford, best-known for producing 4-door Broncos.
CFC: Chlorofluorocarbon. See Refrigerant.
CFI: Central Fuel Injection. AKA CPI, TBI
Chassis: The basic structure of a vehicle, including the suspension & any components that position the suspension. These may include the frame, subframes, unibody, struts, springs, shocks, axles, A-arms, radius arms, watts links, antisway bars, tires, rims, brakes, & bumpers. The powertrain is sometimes considered part of the chassis. Distinguished from the body (except unibody), cabin, interior, & accessories.
Chatter: A fast metallic sound, like a chain rubbing an anvil.
Cherry Bomb: An aftermarket muffler that doesn't actually muffle. It's effectively a straight pipe with a small expansion chamber. The name comes from the red paint.
Chirp: A rapid high-pitched sound, like a small rusty windmill.
CHT: Cylinder Head Temperature.
Chuckle: A rapid nonmetallic noise, like a card against bicycle spokes.
CI: Cylinder Injection; Cubic Inch displacement
CID: Cylinder Identification.
Circuit: A complete electrical path or channel, usually includes the source of electrical energy. Circuit may also describe the electrical path between two or more components. May also be used with fluids, air or liquids.
Circuit Breaker: A mechanical device that automatically opens a circuit when a specific current level is exceeded. They can usually be reset, and some automatically reset after a few moments.
Citizen's Band: 1) A range of radio frequencies near the low end of the spectrum (~27-29kHz) designated by the FCC for free civil use only; 2) A radio that operates in this range, commonly used for communication between heavy trucks on the highway, and also popular among off-roaders.
CKP: Crankshaft Position.
Clang: A heavy metallic sound, like a stone on a metal roof.
Clear Vision: Ford's term for the driver's ability to see the instruments through the steering wheel. If the wheel isn't properly aligned, the spokes will interfere, creating a hazard if the driver leans or swerves to see a gauge.
Click: A slow, light sound, like water dripping on wet carpet.
Clock Spring: A thin coiled (like a clock spring) plastic ribbon containing lines of metal used to electrically connect a rotating object (usually a steering wheel) to a non-rotating object (the steering column). Although a clock spring provides a more stable connection (for airbags) than the older sliding contacts (used for horns & cruise control), it is less reliable over time. The traces of metal often crack, resulting in a failed open circuit.
Closed Loop: A mode of PCM operation during which actator outputs are based on sensor inputs. The PCM enters closed loop after the oxygen sensors are warmed up, and certain other criteria are met. Contrast Open Loop.
Clutch: A mechanical device which uses mechanical, magnetic or friction type connections to facilitate engaging or disengaging of two shafts or rotating members.
Clutch Pedal Position (CPP): A sensor, signal, or circuit which indicates clutch pedal position.
CMP: Camshaft Position.
CMS: Catalyst Monitor Sensor. AKA Downstream HO2S; B1S2 & B2S2.
CMVSS: Canadian Motor Vehicle Safety Standards.
CNG: Compressed Natural Gas. See Natural Gas.
CO: Carbon Monoxide; a colorless, odorless gas that displaces oxygen and bonds to red blood cells, causing unconsciousness & death. It is produced from incomplete (rich) combustion.
CO2: Carbon Dioxide; a colorless, slightly acidic gas produced by combustion & respiration that dissolves easily in water. High concentrations cause difficulty breathing & disorientation.
Coast Clutch Solenoid (CCS): Controls the application and release of the coast clutch in the transmission.
Coffee Can: A steel vacuum reservoir commonly used on '80-95 F-series & Broncos for emissions controls or '80-91 cruise control. They are known to rust, crack, & leak.
Coil: 1. A device consisting of windings of conductors around an iron core, designed to increase the voltage and for use in a spark ignition system; 2. A type of spring constructed as a twisted bar of steel. Its rate is closer to constant over a longer travel than most other types of spring.
Cold-Air Intake: An air intake system (between the atmosphere and the throttle body) which uses ducts to ensure no air is consumed from under the hood. Most manufacturers have used this system since the 70s because cooler outside air is denser, and allows more power to be produced per revolution. Many popular aftermarket air filters defeat this by deleting the factory filter box & ducts. See Open-Element Air Filter.
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.
Collector: The point in an exhaust manifold or header where the tubes join before connecting to the exhaust system.
Combo: Emissions Maintenance Warning/Inferred Mileage Sensor (EMW/IMS) module. A small module attached to certain '87-91 instrument clusters which can be safely deleted.
Companion Flange: A 2-piece connection between a splined shaft & a U-joint in a driveshaft. One piece is a splined disk with a centering hub & several threaded holes for bolts. The other piece captures the caps of the U-joint and bolts to the face of the disk. It is faster to assemble than a yoke, and allows easier adjustment for driveshaft balance.
Compression: A measurement of a cylinder's ability to develop pressure. Although measured in PSIg, the actual number is not significant. Rather the relationship of each cylinder to the others in that engine defines Pass/Fail in a compression test. Actual pressure can vary due to engine temperature, ambient temperature & elevation, engine wear, oil viscosity, & even time since the engine last ran.
Compressor: A mechanical device used to raise the pressure of gasses, usually refrigerant (for HVAC systems) or air (for suspension systems). Contrast Pump.
Computed Timing: The total spark advance in degrees before top dead center. Equals base timing plus/minus an additional factor calculated by the PCM based on input from a number of sensors.
Concours: a vehicle that has been brought to a condition surpassing normal factory production, as it might have appeared in a dealer's showroom when new, or in a museum.
Connector: A device which holds electrical terminals or other ducts in contact so that flow is maintained, generally made of plastic. Electrical connectors generally hold several pairs of terminals and are only necessary during vehicle assembly. Fuel Line Connectors are sometimes metal, and some require special tools & procedures to separate.
Constant Control Relay Module (CCRM): A relay module that provides on-off control of various EEC components.
Constant Velocity (CV) Joint: A universal joint designed to transmit rotation from one shaft to another without affecting the rotational speed the way a Cardan/Hooke's joint does. A Double-Cardan joint approaches CV.
Convertible: A vehicle body designed to be re-configured by the operator, usually by removing or collapsing the roof or a section of the roof. Contrast Coupe, Pickup, Roadster, Sedan, Wagon-body, Truck, Van.
Continuous Memory: The portion of KAM used to store DTCs generated during Continuous Memory Self-Test.
Continuous Memory Self-Test: A continuous test of the EEC system conducted by the PCM whenever the vehicle is operating.
Control: A means or a device to direct and regulate a process or guide the operation of a machine, apparatus or system.
Coolant: The working fluid in heat transfer systems that operate above ambient temperature. Coolants usually contain additives such as rust inhibitors, bittering agents, and ethylene glycol (a sweet-tasting but poisonous antifreeze/antiboil agent). Contrast Refrigerant.
COP: Coil On Plug. An ignition system whose controller is integrated into the PCM, and which uses a separate coil positioned immediately above each spark plug, with no high-voltage wires. See Electronic Ignition System.
Cosmoline: A waxy brown rust preventative for steel parts in storage or shipment, such as new brake rotors & drums. It must be cleaned off before installation.
Cotter Pin: A wire with a semicircular cross-section folded over onto itself & inserted into a small hole through a shaft or bolt to retain another fastener, such as a nut or washer.
Coupe: An enclosed passenger vehicle with 2 doors & a rigid roof structure. Contrast Convertible, Pickup, Roadster, Sedan, Wagon-body, Truck, Van.
CPI: Central Point Injection. AKA TBI, CFI
CPP: Clutch Pedal Position Switch. Located on the clutch pedal and detects when the clutch pedal is depressed.
CPS: Crankshaft Position Sensor/Signal.
CQIS: Common Quality Indicator System.
Crankcase: The enclosed mechanical chambers of an engine which contain lubricating oil & blowby gases, including water, fuel vapor, & soot. Contrast Block. See PCV.
Crankshaft: The part of an engine which converts the reciprocating motion of the pistons to rotary motion.
Crankshaft Position (CKP/CPS): A sensor, signal, or circuit which indicates crankshaft position.
Cribbing: Large heavy shims (usually wood) placed between a large load & the ground, or the load & a jack being used to lift/stabilize it. Wreckers use cribbing to stabilize large overturned vehicles before flipping them upright. A 2x4 used to raise/extend a short jack is cribbing.
Cross-Axled: fully articulated; front suspension at the opposite limit from the rear. AKA Wonky, Crossed Up.
Cross-drilled Rotor: A disk brake rotor which has had holes drilled through both surfaces in a pattern which maintains balance. The purpose is to remove weight from a brake rotor which is larger than necessary for the vehicle. This results from unusually large wheels found on race vehicles, which allow the designer to specify larger rotors. The benefits include: less pedal force; less hydraulic pressure; and less load on the pads & their mountings to achieve the same braking force; all of which allow those components to be lighter. The disadvantage is the higher unsprung weight of the large rotor, and the higher momentum of the spinning tire/rotor assembly. But cross-drilling overcomes both of these by removing unnecessary weight. Because the rotor is oversized to begin with, the loss of some of the friction surfaces is insignificant for light race vehicles. However, removing metal from the disk's surface causes the pads & rotors to wear faster, and causes heat to build up to higher temperatures. Neither of those factors are concerns on race vehicles, but on typical production vehicles, they are. Cross-drilling on street vehicles is cosmetic, and counterproductive to braking efficiency. See Slotted Rotor, Wilwood FAQ.
Crossed Up: fully articulated; front suspension at the opposite limit from the rear. AKA Wonky, Cross-Axled.
Crumple Zone: An area of a chassis OUTside the cabin designed to bear all normal loads, but weak enough to collapse during a collision, allowing more time for the occupants to accelerate (change speed or direction) so they are less likely to come in contact with the cabin. Certain aftermarket equipment (mainly bumpers, brush guards, & trailer hitches) can interfere with this function, causing restraint systems to fail. AKA Accordion.
CSE GND: Case Ground.
CT: Closed Throttle Mode.
CTO: Clean Tach Output. Signal used to drive the instrument panel tachometer.
Cu: Copper.
Curb Idle: PCM controlled idle rpm.
Curb Weight: The actual weight of a regular-production vehicle fully ready to be operated normally, including all fluids & factory-installed optional equipment; but no occupants, cargo, or accessories. Contrast GVW, GVWR.
Custom: The base trim level of Ford trucks for most years, including no options. Compare XL, XLS, XLT, XLT Sport, Nite, Lightning, Eddie Bauer.
CV: 1) Canister Vent; 2) Constant Velocity.
Cylinder Head: A major engine component which covers the outer end of the cylinder(s). It may contain valves, rocker arms, camshafts, lifters or hydraulic lash adjusters, VVTs, spark plugs, glow plugs, injectors, & various sensors and actuators.
Cylinder Head Temperature: A sensor, signal, or circuit which indicates the DRY temperature of the engine cylinder head. Contrast ECT & coolant temperature sender; both of which are immersed in engine coolant.
Cylinder Identification (CID): A signal or circuit which provides crankshaft or camshaft position information for fuel injection synchronization.

[Steve83]

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) combustion code for Diesel Cycle; 2) fuel code for Diesel
Daily Driver: 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.
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; 2) Duty Cycle. The ratio of ON time versus the full cycle period, expressed in percent.
DCL: Data Communication Link. See Data Link Connector.
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): An electrically heated device designed to remove ice, frost or snow from the rear window of the vehicle.
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; 2) Direct Injection (diesel).
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.
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.
Dielectric: Electrically insulating.
Dielectric Grease: Silicone grease used on small 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.
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: 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. 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): 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.
Direct Injection (DI): A diesel 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.
DLC: Data Link Connector. J1962 or EEC-IV connector providing access to vehicle diagnostic information.
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: 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.
DRI: Deposit Resistant Injector. A fuel injector designed to prevent buildup of carbon and other unwanted deposits used since the mid-80s.
Drilled Rotor: See Cross-drilled Rotor.
Driveability: A classification of vehicle concerns, including engine performance, transmission behavior, and drivetrain harshness.
Driveline: 1) See Drivetrain, 2) See Driveshaft.
Driveshaft: 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 clip used on some fuel line fittings, especially fuel filters. It is also used on some coolant fittings. Compare Garter Spring.
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.
Dynamic: Moving/changing. Contrast Static.
E4OD: Electronic 4-speed Overdrive automatic transmission. Renamed 4R100; one of the strongest, longest, & heaviest automatic transmissions ever put in a light truck. Models built before 1995 developed a poor reputation.
E: 1) combustion code for Electric; 2) fuel code for Ethanol
E85: Fuel containing 85% ethanol 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.
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: Engine Coolant Temperature.
EDIS: Electronic Distributorless Ignition System. A system using an independent ignition module and one or 2 coil packs.
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 (DTCs). 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.
EEPROM: Flash Electrically Erasable Programmable Read Only Memory.
EFT: Engine fuel temperature.
EGO: Exhaust Gas Oxygen sensor, signal, or circuit. An early version of a HEGO, without the heater.
EGR: Exhaust Gas Recirculation.
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).
EI: Electronic Ignition.
Electric Air Pump (EAP): An electric pump used in EAIR systems.
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.
Electronic Shift-On-the-Fly (ESOF): A system used to operate the transfer case of a 4WD or AWD vehicle while it is in motion.
Electronic Variable Orifice Steering (EVO): A system or solenoid valve which adjusts the level of assistance provided by the power steering system.
E-Locker: An aftermarket electronically-selectable-locking differential produced by Eaton.
EMI: Electromagnetic Interference. Usually caused by ignition voltage spikes, solenoids, relay operation or noisy generator contacts.
EMW: Emissions Maintenance Warning module. A small module attached to certain '87-91 instrument clusters which can be safely deleted. Compare Combo, IMS. AKA EUL.
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.
EOL: End Of Line. A system designed specifically for use at assembly plants to make sure all new vehicles perform to design specifications.
EPA: Environmental Protection Agency; a government agency which sets & enforces emissions standards in the US.
EPC: Electronic Pressure Control.
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.
ESOF: Electronic Shift-On-the-Fly.
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.
EVO: Electronic Variable Orifice.
EVR: EGR Vacuum Regulator (AKA Exhaust Valve Regulator).
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 or on-road collision. Contrast Step Bar; Nerf Bar; Rock Slider.

[Steve83]

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: assembled, as opposed to being a single piece; welded-together, as opposed to being stamped or machined in 1 piece.
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.
Fan: A device designed to supply a current of air. A fan may also have a frame, motor, wiring harness and the like.
Fan Control (FC): A sensor, signal, or circuit for controlling the engine cooling fan.
Fender: The body panel above the front wheel.
FC: Fan Control.
FCIL: Fuel Cap Indicator Lamp
FDM: Fuel Delivery Module.
FEAD: Front End Accessory Drive belt system.
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.
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 K&N.
Firewall: The body panel between the engine bay & the passenger compartment.
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 Screw. 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.
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.
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. 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: 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 & monocoque. Contrast Unibody.
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.
Freon®: 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.
FSA: Field Service Action. See Recall.
FSC: Fail-Safe Cooling Strategy.
FTP: Fuel Tank Pressure.
Fuel: Any combustible substance burned to provide heat or power. Typical fuels include gasoline and diesel fuel. Other types of fuel include ethanol, methanol, natural gas, propane, hydrogen, oxygen or any combination.
Fuel Delivery Module (FDM): the assembly containing the fuel pump, pickup siphon, pickup screen, reservoir, shuttle valve, & level sender used in most '90-up Fords
Fuel Injector: See Injector.
Fuel Pressure Regulator (FPR): 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 an HO2S 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.
Full-Floating 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.
FWD: Front Wheel Drive. A powertrain system which delivers engine power to a differential in the front axle only. Contrast RWD, AWD, 4WD.

[Steve83]

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.
GE: fuel code for Bi-Fuel, Gasoline/Ethanol.
GEM: Generic Electronic Module.
GEN: Generator.
Generator (GEN): A rotating machine designed to convert mechanical energy into electrical energy. AKA Alternator (a term copyrighted by Chrysler Corporation).
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).
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: A categorization of strength, toughness, durability, heat resistance, & corrosion resistance of fasteners. AKA Material Class in metric fasteners.
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.
Groan: A medium steady rumbling noise, like a continuous zipper.
Grocery-Getter: A disparaging term for a vehicle that LOOKS like an SUV but actually isn't capable of off-roading, hauling, or towing.
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.
Growl: A low steady rumbling noise, like a low note on an electric guitar.
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.
GVW: Gross Vehicle Weight. The maximum allowable curb weight of a vehicle.
GVWR: Gross Vehicle Weight Rating; GVW + cargo load.
Gy: Gray wire or vacuum line.
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.
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.
Harshness: Any momentary sensation that the driver finds objectionable.
HC: 1) Hydrocarbon.; 2) High Compression.
HD: 1) Heavy Duty; 2) Hot-Dipped galvanized.
HCF: Hydraulic Cooling Fan
HCFD: Hydraulic Cooling Fan Drive
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): An Oxygen Sensor (O2S) that is electrically heated. AKA HEGO.
HEGO: Heated Exhaust Gas Oxygen sensor.
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-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: 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.
Hiss: A steady high noise, like an air leak from a tire.
HLA: Hydraulic Lash Adjuster.
HLOS: Hardware Limited Operating Strategy.
HO: High Output.
HO2S: Heated Oxygen Sensor.
Hot Soak: Period of time after an engine operates when its internal heat has not yet dissipated into the environment.
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: 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 (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.
Hum: A low varying noise, like a distant light airplane.
Hydraulic or HydroLock: 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: A mechanism similar to a (solid) lifter which uses engine oil pressure to automatically adjust the valvetrain. AKA Tappet.
HydroBoost: A trademark name for a hydraulic brake booster. Contrast Vacuum Booster.
Hydrogen: A highly flammable gas. 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.
IAB: Idle Air Bypass; see IAC.
IAC: Idle Air Control.
IAT: Intake Air Temperature. AKA ACT
ICM: Ignition Control Module.
IDI: Indirect Injection.
Idle Air Control (IAC): 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.
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.
IMRC: Intake Manifold Runner Control.
IMS: Inferred Mileage Sensor. Compare Combo, EMW.
IMS-EUL: Inferred Mileage Sensor/Extended Useful Life Module. 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): 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 (IMS-EUL): 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: A device for delivering metered pressurized fuel to the intake system or the cylinders. AKA fuel injector.
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, in the air cleaner, 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: International Standards Organization.
IVSC: Integrated Vehicle Speed Control.
IVV: Thermactor Idle Vacuum Valve (carburetor/vacuum)
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.
Kanooter Valve or Kanuter Valve or Kneuter Valve: A joke among mechanics & gearheads to detect amateurs. See KaleCo Automotive.
KAM: Keep Alive Memory.
KAPWR: Keep Alive Power.
KE: Keyless Entry - 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 portion of the memory within the PCM that must maintain power even when the vehicle is not operating. Adaptive strategies & certain fault codes are stored here.
Keep Alive Power (KAPWR): Dedicated, unswitched power circuit that maintains KAM.
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.
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.
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 an triangle, similar in shape to a keystone.
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, 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 Sensor (KS): A peizolectric sensor installed in the engine block which detects any vibration similar to engine knock.
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.

[Steve83]

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.

L: 1) Liters. Metric unit of volume; 2) Left, from the operator's perspective while the vehicle is in motion.
Ladder Frame: The most common style of frame consisting of 2 parallel members (frame rails, roughly horizontal) connected by perpendicular members (crossmembers). The rails & crossmembers may be channels or tubular (boxed). Contrast Unibody, Monocoque.
Lake Pipes: A popular brand of sidepipe, offered as OE on some vehicles like the '67 Corvette L88.
LB: Light Blue wire or vacuum line.
LCD: Liquid Crystal Display.
LCM: Lighting Control Module - an electronic component that controls vehicle lighting, inside & out.
LCV: EGR Load Control Valve (carburetor/vacuum)
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.
Lean: a fuel mixture that has more air than is necessary for the gasoline to burn. 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. Contrast Rich.
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.
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: 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.
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. 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 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. 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: 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.
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.
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.
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.
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.
M: fuel code for Methanol
M5HD: See M5OD.
M5OD: A designation for 3 distinct manual transmissions: the Mazda M5OD-R1 used in mid-sized trucks; the Mazda M5OD-R2 used in fullsize light trucks; and 2 variants of the ZF S5-42 & -45 (both called 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.
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.
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.
MAN VAC: Manifold Vacuum (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 (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.
Mass Air Flow Return (MAF RTN): A return (ground) circuit for the MAF sensor signal.
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 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: Any event in the cylinder that causes a sudden change 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.
MLPS or MLP: Manual Lever Position Switch. See also DTR.
MMO: Marvel Mystery Oil.
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 frame used mostly in race cars & motorcycles consisting of a central structure, roughly tubular, similar to a crane boom. Modern Corvettes & DeLoreans use this. 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.
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.
MY: Model Year.
NAAO: North American Automotive Operations.
NATB: Nationa Auto Theft Bureau.
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.
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, 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.
NOx: Oxides of Nitrogen; the main chemicals responsible for acid rain.
NP 208: 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: 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 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.
NVH: Noise, Vibration, Harshness. A classification of vehicle concerns.
O: fuel code for Other; chemical symbol for Oxygen.
O2S: Oxygen Sensor.
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 of engine coolant.
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.
OC: Oxidation Catalytic Convertor.
OCBR: Oklahoma Classic Broncos Roundup; the 2nd-largest early Bronco off-road event held annually, usually in September at the SuperLift ORV Park in Hot Springs, AR.
OCIL: Overdrive Cancel Indicator Lamp. AKA TCIL
OCS: Overdrive Cancel Switch. AKA TCS
OCT ADJ: Octane Adjust.
Octane Adjust (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.
OHV: Off-Highway Vehicle. AKA Off-Road Vehicle (ORV).
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.
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): A sensor, signal, or circuit which indicates the rotational speed of the transmission output shaft.
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 (O2S): A sensor which detects oxygen (O2) content in the exhaust gases. Compare HEGO, HO2S.
Ozone: A 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.

[Steve83]

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.
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.
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.
PF: Purge Flow.
PFE: Pressure Feedback EGR.
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. Contrast Slotted Screw, Torx.
PI: Performance-Improved; a ~1997 revision to the head design of the 4.6L modular engine standardized ~2001; often confused with Police Interceptor (slang) (a badge on certain Crown Victorias with P71 options).
Pickup or Pickup Truck: A light truck with a cab separate from its cargo bed. Contrast Convertible, Coupe, Roadster, Sedan, Wagon-body, Truck, Van.
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.
PIP: Profile Ignition Pickup.
Pitman Arm: A steering mechanism which converts the rotating motion of the steering shaft into the swinging of an arm. Contrast Rack & Pinion.
Pk: Pink wire or vacuum line.
PL: Power Door Locks
PM: Power Mirrors
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).
Polished: A grinding & sanding process inside a manifold or head port to remove roughness from casting, and thereby improve 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.
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 flow, and thereby improve power & economy.
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) create a portal configuration.
Posi: (slang) Positraction.
Positive Crankcase Ventilation (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: An adjustable resistance component commonly used as a position sensor for rotatable shafts (Example: TP Sensor). AKA Pot, 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 powered by the FEAD supplying pressure to a gear box 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 (PFE): An EGR system that monitors EGR pressure to control EGR flow.
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): 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: 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 Teflon®, 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.
Purge Flow (PF): Amount of fuel vapor burned in the engine.
Pump: A device used to raise, transfer, or circulate fluids at a relatively constant pressure. Contrast Compressor.
PVC: PolyVinyl Chloride; a common type of plastic. Often confused with PCV.
PW: 1) Power Windows; 2) Pulse Width.
PWM: Pulse Width Modulation.
PWR GND: Power Ground.
Quarter (Panel): The body panel behind 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.

[Steve83]

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.
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.
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.
Red Wrench: (slang) Torch, usually acetylene.
Recall: 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. Contrast TSB.
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.
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 (Suva®DuPont), a non-chlorinated hydrofluorocarbon (HFC); older systems used R-12 (Freon®DuPont), 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 connections in one circuit are opened or closed by changes in another circuit. Almost all Ford vehicles use a starter relay, 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.
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.
RF: Radio Frequency. A band of electromagnet frequencies between ultrasonic & microwave.
RFI: Radio Frequency Interference. A high-frequency form of EMI.
Return (RTN): A dedicated sensor ground circuit.
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 gasoline to burn completely. 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.
RITS: Run In The Sun; an off-road event for Bronco owners & their friends held each year in the SouthEast.
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.
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.

[Steve83]

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) combustion code for Otto 4-Stroke-Cycle Piston engines.
SAE: Society of Automotive Engineers, now SAE International.
Safety Certification Label: 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.
SCDS: Speed Control Deactivator Switch; the secondary (failsafe) cruise control cancel switch. An early type is the subject of a massive recall due to fires.
SCP: Standard Corporate Protocol.
Screw: 1) A typically light-duty fastener, 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: 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.
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: Secondary Equipment Manufacturers' Association. A trade guild of businesses who supply non-OE parts, OR a trade show they host each year.
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 sections: 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. A sensor is typically an analog device. Its digital counterpart is a switch.
Sensor Ring: See Tone Ring.
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. 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 form has a high dielectric, and is often referred to as "dielectric grease".
Single-Function Reservoir (SFR): A fuel reservoir used on '84-89 single-tank Ford trucks which may contain a filter.
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.
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.
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
Sniffer: 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.
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 a starter with a solenoid, 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 on the pinion shaft, technically called pinion gears. They mesh with the side gears and are responsible for the differential action.
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.
SS: 1) Shift Solenoid; 2) Super Sport; a high-performance vehicle, usually a V8 coupe (muscle car).
ST: Scan Tool.
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.
Static: Unmoving/stagnant/still. Contrast Dynamic.
Step Bar: A light 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 truck maker 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.
Stupid Tax: (slang) the cost of vehicle repairs, usually those due to exuberant driving.
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 owner isn't aware of sublet jobs because the primary shop handles the transportation & warranty. 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 body) 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.
Suva®: The DuPont name for R-134a. See Refrigerant.
SV CBV: Solenoid Valve Carborator Bowl Vent (carburetor/vacuum)
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.

[Steve83]

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.

T: 1) combustion code for Turbine; 2) Tan wire or vacuum line.
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: Thermactor Air Diverter
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: a branch of a wiring harness.
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: 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.
Teflon®: See PTFE.
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.
Test: A procedure whereby the performance of a product is measured under various conditions.
Thermactor Air Bypass (TAB): A signal, circuit, solenoid valve, vacuum line, or air valve which directs the output of the secondary air pump either to the TAD or to an exhaust muffler.
Thermactor Air Diverter (TAD): A signal, circuit, solenoid valve, vacuum line, or air valve which directs the flow of secondary air either to the exhaust manifolds (upstream) or to the catalytic converter (downstream), through a check valve in either case.
Thermistor: A temperature dependent resistor, like that used in CHT and ECT sensors.
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): A sensor, signal, or circuit which indicates the position of the throttle plate.
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.
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.
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.
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)
Tone Ring: 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).
TFT: Transmission Fluid Temperature.
TLEV: Transitional Low Emission Vehicle.
TP: Throttle Position.
TR: Digital Transmission Range sensor.
TracLok: Traction Lok
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.
TRE: Tie rod end.
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: 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: Twin Traction Beam.
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(TTB): 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. 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.

[Steve83]

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.
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: Violet (purple) wire or vacuum line.
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: A power-assist mechanism for vehicle brakes which uses vacuum pressure to amplify the force applied to the brake master cylinder. Contrast HydroBoost.
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 or a steel can) to provide vacuum for actuators during conditions when engine-generated vacuum may not be available.
Vacuum Tree: A vacuum manifold with several nipples radiating from a central fitting.
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 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.
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)
VDF: Visctronic Drive Fan. An electrically-assisted viscous fan coupling.
VDV: Vacuum Delay Valve; Vacuum Diverter Valve (carburetor/vacuum)
VECI Label: Vehicle Emission Control Information Label. A sticker showing vehicle-specific information, codes, & diagrams describing the factory-installed emissions systems, and tune-up information.
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 & speed sensor on the speedometer cable. Later types use an electronic servo & 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 or Signal (VSS): A sensor, signal, or circuit which provides vehicle speed information. Until ~1989, this was used exclusively by the VSC, and from '89~92 it was also used for E4OD control on F-series trucks. It is typically installed in the speedometer cable, the transmission tailhousing, or the transfer case rear output housing. Contrast ABS(2).
VFD: Vacuum-Fluorescent Display.
Vibration: Any continuous sensation that a vehicle occupant finds objectionable.
VIN: 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: See Safety Certification Label.
Viscosity: 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.
VOM: Volt-Ohm Meter. Non-specific, so generally used for analog (needle) meters to differentiate from DVOMs & DMMs (DIGITAL meters).
VPWR: Vehicle Power.
VRDV: Distributor Vacuum Retard Delay Valve (carburetor/vacuum)
VREF: Reference Voltage, generally ~5VDC supplied from the PCM to certain transistorized sensors.
VSC: Vehicle Speed Control.
VSS: Vehicle Speed Sensor (early); Vehicle Speed Signal (late).
W: White wire or vacuum line.
WAC: Wide Open Throttle A/C Cut-off.
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 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.
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.
Weekend Warrior: 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: 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.
Wonky: 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.
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.
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).
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".

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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