Automotive A to Z™

4EAT – Ford electronic automatic 4 speed transaxle.

A – Amperes

A/C – Air Conditioning

A/C CLUTCH SWITCH – Device which sends a signal to the vehicle's on-board computer to prevent engine idle speed from varying when the compressor clutch cycles. The computer activates the AIS motor to give a one-time increase in engine speed when the A/C clutch engages.

A/C CUT-OUT RELAY – Device which operates under control of the vehicle's on-board computer to prevent compressor clutch engagement under wide open throttle conditions.

A/C SWITCH – Device which sends a signal to the vehicle's on-board computer to indicate the air conditioner is operating. The computer increases engine speed to compensate for the additional load. (This signal was not used on 1984-85 EFI models).

A/CL BIMET – Air Cleaner Bi-Metal Sensor

A/CL DV – Air Cleaner Duct and Valve Vacuum Motor

A/D – Analog to Digital Converter

A/F – Air Fuel Ratio

A/T – Automatic Transmission

A4LD – Ford automatic 4 speed lock-up converter drive.

A4R70W – Automatic Overdrive Electronic Wide Ration Transmission

AAC – Auxiliary Air Control

AAV – Anti-Afterburn Valve (Mazda)

ABCV – Airbleed Control Valve (Ford)

ABS – Antilock Brake System

ABSV – Air Bypass Solenoid Valve (Mazda)

ABV – Air Bypass Valve

AC – Alternating Current

ACC – Air Conditioning Clutch

ACC – Automatic Climate Control

ACCS – Air Conditioning Cycling Switch.

ACD – Air Conditioning Demand Switch

ACON – Air Conditioning On Signal

ACP – Air Conditioning Pressure Signal

ACPSW – Air Conditioning Pressure Switch

ACR – Air Conditioning Relay

ACR4 – Air Conditioning Refrigerant, Recovery, Recycling, Recharging

ACT – Air Charge Temperature sensor or signal circuit.

ACTUATION TEST MODE (ATM) – The diagnostic mode used by the vehicle's on-board computer to activate and deactivate specific output circuits to determine if they are operating properly. Outputs of this test mode are displayed as 2-digit ATM codes which identify malfunctions to a specific circuit.

ACTUATOR – A device that moves or controls another device in response to a mechanical, hydraulic, pneumatic, or electrical input.

ACV – (Thermactor) Air Control Valve.

A-D (ANALOG-DIGITAL) CONVERTER – An electronic circuit which converts an analog input to a digital output.

ADU – Analog-Digital Unit

AFC – Air Flow Control

AFM – Air Flow Meter

AFR – Air Fuel Ratio

AFS – Air Flow Sensor (Mitsubishi)

AFTER TOP DEAD CENTER – Refers to crankshaft position relative to the ignition timing in degrees.

AICV (AIR INJECTION CHECK VALVE) – One-way check valve which prevents hot exhaust gases from backing up in the hose and air pump in the event of air pump belt failure, abnormally high exhaust system pressure, or if the air hose ruptures.

AIR – Secondary air injection (formerly thermactor).

AIR BPV – Thermactor Air Bypass Valve.

AIR CHARGE TEMPERATURE SENSOR – A thermistor (temperature-controlled variable resistor) located in the intake manifold.

AIR CLEANER VACUUM DIAPHRAGM – A diaphragm, controlled by the air temperature sensor, which controls the position of the door in the air cleaner duct to allow warm or cold air into the carburetor.

Air Conditioning Clutch – Sends signal input to computer relating status of air conditioning clutch.

AIR GAP – The space between the spark plug electrodes, motor and generator armatures, field shoes, etc.

AIR RELIEF VALVE (ARV) – Device which vents excess air pump output into the engine compartment when a specified discharge pressure is reached.

AIR SWITCHING/RELIEF VALVE (ASRV) – The ASRV directs air injection to the exhaust port or downstream injection port, depending on engine operating temperature, and regulates system pressure by controlling air pump output at high engine speeds (when pressure reaches a predetermined level, some of the air pump output is vented to atmosphere. Initially air injection is directed to the exhaust ports; as the engine reaches normal operating temperature, air injection is directed to the downstream injection port for proper system operation.

AIR/FUEL (AF) MIXTURE – A ratio of the amount of air that is mixed with fuel before it is burned in the combustion chamber.

AIRB – Air Bypass Solenoid

AIRD – AIR Diverter Solenoid

AIS – Air Injection System (Chrysler)

AIS – Automatic Idle Speed

AIS (AUTOMATIC IDLE SPEED) MOTOR – Increases or decreases the size of an idle air bypass to raise or lower idle speed. The AIS motor is mounted on the throttle body assembly and is controlled by the vehicle's on-board computer.

AIV – Air Injection Valve

ALC – Automatic Level Control

ALCL – Assembly Line Communications Link (GM)

ALDL – Assembly Line Data Link

ALT – Alternator (replaced with GEN)

ALTERNATING CURRENT (AC) – An electrical current which alternates it's direction of flow at regular intervals.

AM1 – Air Management 1, AIR Bypass

AM1 – Thermactor Air Management (TAB).

AM2 – Air Management 2, AIR Diverter

AM2 – Thermactor Air Management (TAD).

AMB – Ambient

AMBIENT TEMPERATURE – Temperature of air surrounding an object.

AMMETER – A device which measures current in an electrical circuit.

AMPERAGE – The total amount of current flow in a circuit.

AMPERE – A unit of measurement to determine the current (flow of electrons) in a circuit.

AMPLIFIER – An electronic device (usually a vacuum tube or transistor) used in a circuit to increase voltage or current.

AMPLITUDE – The maximum rise and fall of a voltage signal from its average value.

ANALOG – A method of transmitting information by varying a voltage or current.

ANALOG CONTROLS – Circuits which process and/or transmit information by varying a current or voltage.

ANALOG VOLT-OHMMETER (VOM) – A device which measures voltage and resistance in an electrical circuit. Readings are displayed by a meter movement (instead of a digital display).

ANALOG-DIGITAL (A-D) CONVERTER – An electronic circuit which converts an analog input to a digital output.

ANTI-BFV – Anti-Backfire Valve.

AOD – Automatic Over Drive transmission.

AODE – Automatic Overdrive Electronic Transmission

AODE-W – Automatic Overdrive Electronic Wide (ratio transmission)

AP – Accelerator Pedal

APC – Automatic Performance Control

APS – Absolute Pressure Sensor (GM)

APS – Atmospheric Pressure Sensor (Mazda)

APT – Adjustable part Throttle

ARC – Automatic Ride Control

ARMATURE – The moveable part of an electromagnetic device; the rotating part of a generator or motor.

ARS – Automatic Restraint System

ASARC – Air Suspension Automatic Ride Control

ASD – Automatic Shutdown Relay

ASDM – Airbag System Diagnostic Module (Chrysler)

ASE – Automotive Service Excellence

ASM – Acceleration Simulation Mode

ASR – Acceleration Slip Regulation

ATC – Automatic Temperature Control

ATDC – After Top Dead Center

ATF – Automatic Transmission Fluid

ATM – Actuator Test Mode

ATMOSPHERIC PRESSURE – The pressure caused by the weight of the earth's atmosphere; equal to approximately 14.69 psi at sea level.

ATOMIZATION – To reduce a liquid to a fine spray.

ATS – Air Temperature Sensor (Chrysler)

ATX – Automatic Transaxle

AUTOMATIC SHUT-DOWN RELAY – Operates under control of the vehicle's on-board computer to supply voltage to the in-tank fuel pump, ignition coil and fuel injectors during engine cranking.

AVAILABLE VOLTAGE – The amount of voltage measured at the voltage source, or other point in a circuit, with respect to ground.

AVOM – Analog Volt/Ohm Meter.

AWD – All-Wheel Drive

AWG – American Wire Gage'

AX4S – Automatic 4-Speed Trans.

AXOD – Automatic Overdrive transaxle.

AXOD-E – Automatic Overdrive Transaxle - Electronically Controlled

B/MAP – Barometric/Manifold Absolute Pressure

B+ – Battery Positive Voltage - The voltage or potential of the battery positive terminal.

BAC – Bypass Air Control Valve

BARO – Barometric Pressure

BAROMETRIC (BARO) READ SOLENOID – The BARO read solenoid is a solenoid located in the MAP sensor vacuum line and provides an indication of barometric pressure (on turbocharged vehicles) to the vehicle's on-board computer for boost control.

BASE IDLE – Idle RPM when the throttle lever rests on the throttle stop and the Idle Speed Control is fully retracted and disconnected.

BAT – Battery

BATTERY – A group of two or more chemical cells connected together for the production of an electric current.

BATTERY TEMPERATURE SENSOR – The sensor is a 10K ohm thermistor (temperature-controlled variable resistor), located in the vehicle's on-board computer, which controls charging system voltage according to battery temperature (resistance decreases as temperature increases).

BATTERY VOLTAGE – The voltage measured between the two terminals of a battery.

BATTERY-HOT – Describes a circuit which receives input voltage directly from the starter relay terminal. Voltage is available whenever the battery is charged.

BC – Blower Control

BCM – Body Computer Module.

BEFORE TOP DEAD CENTER (BTDC) – Refers to crankshaft position relative to the ignition timing in degrees.

BHP – Brake Horsepower

BHS – Bimetal Heat Sensor (Ford)

BID – Breakerless Inductive Discharge (AMC)

BIMETAL – A contact arm made of two dissimilar metals, each having a different expansion rate. Heat causes bending movement of the arm to make or break a circuit.

BLM – Block Learn Multiplier (replaced with LT FUEL TRIM)

BLOWN – Describes an open (melted) fuse filament, caused by excessive current draw.

BMAP – Barometric/Manifold Absolute Pressure Sensor (Ford)

BOB – Breakout Box

BOO – Brake On-Off input to the computer.

BOOST – Condition of over-pressure (above atmospheric) in the intake manifold; caused by intake air being forced in by a turbocharger or supercharger.

BP – Barometric Pressure sensor. Used to compensate for altitude variations.

BP – Barometric Pressure

BPA – ByPass Air solenoid.

BPA – Mechanical Bypass Air

BPCSV – Bypass Control Solenoid Valve

BPP – Brake Pedal Position Switch

BPS – Back Pressure Sensor

BPT – Back-Pressure Transducer

BPV – Bypass Valve (Ford)

BPW – Brake Pulse Width

BRAKE SWITCH – Device which provides a signal to the vehicle's on-board computer to determine idle throttle position (in the event the electronic idle switch malfunctions).

BSV – Backfire Suppressor (Ford)

BTDC – Before Top Dead Center

BTS – Battery Temperature Sensor

BTSI – Brake Transmission Shift Interlock

Btu – British Thermal Unit

BUS N – Bus Negative

BUS P – Bus Positive

BV – Bowl Vent Port (Ford)

BVP – Backpressure Transducer Valve

BVSV – Bi-Metal Vent Control Valve

BVT – Backpressure Variable Transducer System (Ford)

C – Carbon

C – Celsius

C.A.R.B. – California Air Resource Board

C3 – Computer Command Control System (GM)

C3I – Computer Controlled Coil Ignition. Produces ignition spark without aid of an ignition distributor.

C4 – Computer Controlled Catalytic Converter System (GM)

CAC – Charge Air Cooler

CALIBRATION – The act of adjusting or verifying test instrument accuracy in relation to the graduations used on the instrument.

CANISTER – A charcoal-filled container in an evaporative emission control system which traps vapors from the fuel system.

CANISTER PURGE CONTROL VALVE (CPCV) – A vacuum-operated valve which controls the flow of vapors from the canister to the engine. At engine temperatures below 145℉ (61℃), the vehicle's on-board computer de-energizes the solenoid to allow vacuum to flow to the purge valve; the valve then purges fuel vapors through the throttle body.

CANISTER PURGE SOLENOID – Electrical solenoid or its control line. Solenoid opens a valve from fuel vapor canister line to intake manifold when energized. Controls flow of vapors between carburetor bowl vent and carbon canister.

CANP – EVAP Canister Purge Solenoid

CAPACITANCE – The property of a condenser (capacitor) which enables it to hold an electric charge.

CAPACITOR – A device capable of storing an electric charge.

CAPACITY – The amount of electricity which can be delivered, under specific conditions, at a given rate of discharge. Capacity is generally specified in amp-hours.

CARB – California Air Resources Board

CARB – Carburetor

CAS – Clean Air System

CAS – Crank Angle Sensor

CASE – Cranking Angle Sensing Error

CATALYTIC CONVERTER – Muffler like assembly placed in exhaust system that contains a catalyst to change hydrocarbons and carbon monoxide into water vapor and carbon dioxide.

CBD – Closed Bowl Distributor

CC – Catalytic Converter

CC – Climate Control

CC – Cruise Control

CC – Cubic Centimeters


CCC – Computer Command Control System (GM)

CCC – Converter Clutch Control solenoid or its circuit.

CCD – Chrysler Collision Detection

CCD – Computer Controlled Dwell, used on Ford Vehicles.

CCD BUS – A communication line used by various on-board computers for the transmission of data.

CCDIC – Climate Control Driver Information Center

CCEI – Coolant Controlled Idle Enrichment (Chrysler)

CCEV – Coolant Controlled Engine Vacuum Switch (Chrysler)

CCM – Central Control Module

CCM – Continuous Component Monitor

CCNT, DTC CCNT – Count Code

CCO – Converter Clutch Override

CCOT – Cycling Clutch Orifice Tube

CCP – Climate Control Panel

CCP – Controlled Canister Purge (GM)

CCRM – Constant Control Relay Module

CCS – Coast Clutch Solenoid

CCSP – Carbon Canister Storage/Purge

CCV – Canister Control Valve

CDCV – Canister Drain Cut Valve

CDI – Capacitor Discharge Ignition (AMC)

CDR – Chrysler Diagnostic Readout

CDRV – Crankcase Depression Regulator Valve

CE – Commutator End

CEAB – Cold Engine Air Bleed

CEC – Crankcase Emission Control System (Honda)

CECU – Central Electronic Control Unit (Nissan)

CEL – Check Engine Light

CENTRAL FUEL INJECTION – Computer control fuel injection at throttle body, used on Fords, same as throttle body injection.

Central Fuel Injection – Ford brand name for Throttle body Fuel Injection.

CER – Cold Enrichment Rod (Ford)

CES – Clutch Engage Switch

CESS – Cold Engine Sensor Switch

CFC – Chlorofluorocarbons

CFI – Central Fuel Injection

CFI – Continuous Fuel Injection

CFM – Cubic Feet Per Minute

CFV – Critical Flow Venturi

CHARGE – Any condition where electricity is available. Also describes the process of restoring the active materials in a battery cell by electrically reversing the chemical action.

CHARGE TEMPERATURE SENSOR – A thermistor (temperature-controlled variable resistor) which provides varying voltage signals, in proportion to intake manifold air temperature, to the vehicle's on-board computer. The computer uses this signal to control the air switching, EGR and spark advance systems.

CHARGE TEMPERATURE SWITCH – An "ON-OFF" switch which controls EGR flow (closed = no flow permitted, open = flow permitted).

CHARGING VOLTAGE – The voltage present at the alternator output.

CHECK ENGINE LIGHT – Instrument panel light used either to aid in identification and diagnosis of malfunctions, or to indicate maintenance is required.

CHECK VALVE – A one-way valve which allows vacuum or gas flow in one direction only.

CHM – Cold Mixture Heater

CID – Cubic Inch Displacement

CID – Cylinder Identification sensor or its circuit.

CIRCUIT – An arrangement of conductors and components through which current can flow.

CIRCUIT BREAKER – A device (other than a fuse) which interrupts current flow in a circuit under abnormal conditions.

CIS – Continuous Injection System (Bosch)

CKP – Crankshaft Position Sensor

CKP REF – Crankshaft Position Reference

CKT – Circuit

CL – Closed Loop

CLC – Converter Lockup Clutch (replaced with TCC)

CLCC – Closed Loop Carburetor Control

CLNT – Coolant

CLOSED CIRCUIT – An uninterrupted path beginning at the current source and returning to the current source.

CLOSED LOOP – A circuit in which the output of an electronic control is measured by a sensor and is returned to the control to indicate if the output is optimum or excessive.

CLV – Calculated Load Value

CMFI – Central Multi-port Fuel Injection

CMP – Camshaft Position Sensor

CMP REF – Camshaft Position Reference

CO – Carbon Monoxide

CO2 – Carbon Dioxide

COC – Conventional Oxidation Catalyst (Ford)

COC (CONVENTIONAL OXIDATION CATALYST) – Component of an emission control system which acts on the pollutants HC and CO.

COMBUSTION CONTROL COMPUTER – A computer control system used on 1981-83 Imperial models with electronic fuel injection to control fuel injection, spark timing and advance, idle speed, air injection switching, and fuel evaporation purging.

COMMON POINT – A terminal or connection where two parallel circuits or components are joined.

Computer Control System – An electronic control system, consisting of an on-board computer and related sensors, switches and actuators, used to ensure peak performance and fuel efficiency while reducing pollutants in the vehicle's emissions.

COMPUTER TIMING – Total spark advance in degrees before top dead center. Calculated by Ford EEC-IV processor, based on sensor input.

CONDENSER – A device capable of storing an electric charge.

CONDUCTOR – Any material or substance (solid, liquid or gas) capable of transmitting electricity.

CONNECTOR – A mechanical device used to connect the components of an electrical circuit together.

CONTINUITY – A condition where a circuit, or part of a circuit is closed or continuous between given points.

CONTINUOUS SELF-TEST – Continuous test of Ford EEC-IV system conducted whenever vehicle is in operation.

CONTROLLER – Generic name for an on-board solid state microcomputer which monitors engine conditions and controls certain engine functions. Specific computers such as ECU, Power Module, Logic Module, SBEC and SMEC are generically referred to as controllers.

Converter Clutch Override – Output from the computer processor to the transmission.

COOLANT TEMPERATURE SENSOR (CTS) – A thermistor (temperature-controlled variable resistor) which provides varying voltage, in proportion to engine coolant temperature, to the vehicle's on-board computer.

COOLANT TEMPERATURE SWITCH – An "ON-OFF" switch which measures the engine coolant temperature and transmits the information on to the vehicle's on-board computer. The coolant temperature switch is closed when engine coolant is cold.

COOLANT VACUUM SWITCH COLD CLOSED (CVSCC) – A switch mounted in the thermostat housing, which closes when coolant temperature is cold, to prevent EGR flow. The switch opens when coolant temperature is warm, to allow EGR flow.

COOLANT VACUUM SWITCH COLD OPEN (CVSCO) – A switch mounted in the thermostat housing, which opens when coolant temperature is cold, to allow manifold vacuum into the air delivery switching system. The switch closes when coolant temperature is warm, to prevent manifold vacuum from entering the air delivery switching system.

COP – Coil On Plug Electronic Ignition

CORE – The center conductor part of a wire, or the iron magnetic material of a solenoid magnet.

CP – Canister Purge (GM)

CP – Crankshaft Position Sensor (Ford)

CPA – Connector Position Assurance

CPI – Central Port Fuel Injection

CPP – Clutch Pedal Position

CPS – Central Power Supply

CPS – Crankshaft Position Sensor. Provides the ECU with engine speed and crankshaft angle (position).

CPSOV – Canister Purge Shut Off Valve (Ford)

CPU – Central Processing Unit

Crankshaft Position Sensor – Provides the ECU with engine speed and crankshaft angle (position).

CRK – Cranking Signal

CROSS-CIRCUIT SHORT – A current flow path between the hot wires in two different circuits.

CRT – Cathode Ray Tube

CSC – Coolant Spark Control (Ford)

CSE GND – PCM Case Ground

CSSA – Cold Start Spark Advance System (Ford)

CSSH – Cold Start Spark Hold System (Ford)

CTAV – Cold Temperature Actuated Vacuum Switch (Ford)

CTM – Central Timer Module

CTO – Clean Tachometer Output

CTO – Coolant Temperature Override

CTOX – Continuous Trap Oxidizer

CTP – Closed Throttle Position

CTS – Charge Temperature Switch (Chrysler)

CTS – Coolant Temperature Sensor.

CTVS – Closed Throttle Vacuum Switch

CURB IDLE – Computer controlled idle rpm.

CURRENT – The movement of electrons through a conductor material.

CURRENT-LIMITING RESISTOR – A resistor in a circuit to which limits the current.

CV – Constant Velocity

CV – Control Valve

CVCC – Compound Vortex Controlled Combustion System (Honda)

CVR – Control Vacuum Regulator (Ford)

CVS – Constant Volume Sampler

CWM-Ford – Cold Weather Modulator (Ford)

CYCLE – A complete alternation in an alternating current.

CYLINDER IDENTIFICATION SIGNAL (CID) – A signal generated by crankshaft timing sensor, used to synchronize ignition coils, due to the fact that some models use a 2 ignition coil pack DIS system.

DAB – Delayed Accessory Bus

Data Output Line to IPC – Fuel calculation data from EEC-IV processor to trip computer.

DATA OUTPUT LINK (DOL) – Data Output Link. Fuel calculation data from EEC-IV processor to trip computer.

dB – Decibels

DC – Direct Current

DC – Duty Cycle

DCISCA – DC Motor Idle Speed Actuator

DCL – Data Communication Link

DDL – Diagnostic Data Link

DE – Drive End

DEAD SHORT – A short circuit having zero resistance.

DEC – Digital Electronic Controller

DE-ENERGIZED – The condition of an electrical circuit having the electric current or energy source turned off.

DEFI – Digital Electronic Fuel Injection (Cadillac)

DEPS – Digital Engine Position Sensor

DERM – Diagnostic Energy Reserve Module and air bag (SIR) controller.

DETONATION (KNOCK) SENSOR – A piezoelectric device which responds to spark knock (caused by over-advanced ignition timing) and transmits this information to the vehicle's on-board computer. The computer uses this signal to retard ignition timing during knock conditions.

DFCO – Decel Fuel Cutoff Mode

DFI – Direct Fuel Injection

DFS – Decel Fuel Shutoff

DI – Direct Ignition

DI – Distributor Ignition (System)

DIAGNOSTIC MODE – The mode of operation used by the vehicle's on-board computer to transmit Fault Codes (representing vehicle malfunctions). The computer retains Fault Codes for malfunctions which have occurred in the last 50 ignition cycles.

DIAGNOSTIC READ-OUT BOX (DRB) – The Chrysler Motors tester used to diagnose the on-board computer system. The DRB displays specific values in various modes, and displays Fault Codes, to assist the technician in diagnosing and correcting vehicle malfunctions.

DIAPHRAGM – A mechanical component which moves a control lever when a vacuum signal is applied.

DIC – Driver Information Center

DICM – Distributor Ignition Control Module

DID – Driver Information Display.

DIELECTRIC – The insulating material used between the plates of a capacitor or condenser.

DIGITAL CONTROLS – Circuits which process and/or transmit information by switching current on and off.

DIGITAL INJECTION – Cadillac brand name for Throttle body Fuel Injection.

DIGITAL VOLT-OHMMETER (DVOM) – A device which measures voltage and resistance in an electrical circuit. Readings are displayed in digital form on a liquid crystal display (LCD).

DIGITAL VOLT-OHMMETER (HIGH IMPEDANCE) – This voltmeter has high opposition to the flow of electrical current, making it ideal for electrical measurements in circuits with low current flow (such as those found in electronic systems).

DIODE – An electronic component which allows current flow in one direction and insulates (blocks current flow) in the opposite direction.

DIRECT CURRENT (DC) – Electrical current which flows in one direction only.

Direct Ignition (Waste Spark) – Produces ignition spark without aid of an ignition distributor. (Similar to C3I).

DIRECT IGNITION SYSTEM (DIS) – Produces ignition spark without the aid of an ignition distributor.

DIRECT IGNITION SYSTEM (DIS) – Produces ignition spark without the aid of an ignition distributor.

DIS – Direct Ignition (Waste Spark)

DISTANCE (SPEED) SENSOR – Sensor is mounted at the transaxle tailshaft housing which transmits a signal representing vehicle speed to the vehicle's on-board computer.

DISTRIBUTOR – A device which directs secondary current from the induction coil to the spark plugs of a multi-cylinder engine, in proper firing order.

DIY – Do-It-Yourself

DLC – Data Link Connector (OBD)

DM – Drive Motor

DMCM – Drive Motor Control Module

DMCT – Drive Motor Coolant Temperature

DMPI Module – Drive Motor Power Inverter Module

DMS – Distributor Modulator System

DOHC – Dual Overhead Cam

DOL – Data Output Line to IPC

DPC – Dynamic Pressure Control

DPDIS – Dual Plug Distributorless Ignition System, used on some Ford 2.3L engines.

DPFE – Differential Pressure Feedback

DPI – Dual Plug Inhibit, used on some Ford 2.3L engines.

DRAW – The amount of electric current used by a load or circuit.

DRB II – Diagnostic Readout Box (Chrysler)

DRCV – Distributor Retard Control Valve

Drive Cycle – An extended set of driving procedures that takes into consideration the various types of driving conditions encountered in real life.

DRIVER – A transistor used to open and close the ground circuit of an output device (solenoid, relay, etc.)

Driving Condition – A specific environmental or operation condition under which a vehicle is operated; such as starting the vehicle when cold, driving at steady speed (cruising), accelerating, etc.

DRL – Daytime Running Lights

DSO – Digital Storage Oscilloscope

DSR – Ford Diagnostic Subroutine

DSS – Downshift Solenoid

DSSA – Dual Signal Spark Advance (Ford)

DSV – Deceleration Solenoid Valve

DTC FRZ – Diagnostic Trouble Code Freeze Frame

DTC(s) – Diagnostic Trouble Code(s)

DTM – Diagnostic Test Mode

DTVS – Dual Temperature Vacuum Switch

DUAL CATALYTIC CONVERTER – Combines 2 converters in one shell. Controls NOx, HC and CO. Also called TWC.

DURA SPARK SYSTEM – The Ford ignition system used with the 5.8L feedback carbureted MCU control system.

DUTY CYCLE – The percentage of time that the vehicle's on-board computer energizes a solenoid.

DV – Delay Valve

DV TW – Delay Valve, 2 Way.

DVAC – Distributor Vacuum Advance Control Valve

DVDSV – Differential Vacuum Delay and Separator Valve

DVDV – Distributor Vacuum Delay Valve

DVM (10 MEG) – Digital voltmeter with a minimum of 10 million ohms resistance. Allows measurement in circuit without affecting the circuit operation.

DVOM – Digital Volt-Ohmmeter

DV-TW – Relay Valve Two Way

DVVV – Distributor Vacuum Vent Valve

DWELL – Amount of time (recorded on a dwell meter in degrees) that current passes through a closed switch.

E4OD – Electronic 4-Speed Overdrive

EAC – Electronic Air Control (replaced with AIR)

EACV – Electronic Air Control Valve

EAIR – Electronic Secondary Air Injection

EAS – Electronic Air Switching, directs airflow to catalytic converter or exhaust ports of the engine.

EBCM – Electronic Brake Control Module

EBP – Exhaust Back :Pressure

EBTCM – Electronic Brake T/C Module

EC – Engine Control

ECA – Electronic Control Assembly. Ford's engine controlling computer.

ECC – Electronic Climate Control

ECCS – Electronic Concentrated Control System

ECI – Extended Compressor at Idle

ECIT – Electronic Control Ignition Timing

ECL – Engine Coolant Level

ECM – Engine Control Module properly call a Powertrain Control Module.

ECS – Emission Control System

ECS – Evaporation Control System (Chrysler)

ECT – Engine Coolant Temperature sensor or circuit.

ECU – Electronic Control Unit

EDF – Electro-Drive Fan relay or its circuit.

EDIS – Electronic Direct Ignition System (replaced with EI)

EDM – Electronic Distributor Modulator (Ford)

EEC – Electronic Engine Control (Ford)

EEC-I – Control of Ignition Timing

EEC-II – Control of Ignition Timing and Fuel Delivery Through a Feed Carburetor System

EEC-III – Control of Ignition Timing and Fuel Delivery Through a Central Fuel Injection System

EEC-IV – Electronic Engine Control design 4. A computer controlled system of engine control used on Ford. Control of Ignition Timing and Fuel Delivery Through an Electronic Fuel Injection System

EECS – Evaporative Emission Control System

EEGR – Electronic Exhaust Gas Recirculation valve (Sonic).

EEGR Monitor – Electronic EGR Test

EEPROM – Electronically Erasable Programmable Read Only Memory

EESS – Evaporative Emission Shed System (Ford)

EET – Electronic Exhaust Gas Recirculation Transducer.

EEVIR – Evaporator Equalized Values in Receiver

EFC – Electronic Feedback Carburetor (Chrysler)

EFC – Electronic Fuel Control

EFCA – Electronic Fuel Control Assembly (Ford)

EFE – Early Fuel Evaporation

EFI – Electronic Fuel Injection

EFT – Engine Fuel Temperature

EFV – Early Fuel Evaporation

EGC – Exhaust Gas Check Valve (Ford)

EGO – Exhaust Gas Oxygen Sensor (Ford)

EGOR – EGO Signal Return (Ford)

EGR – Exhaust Gas Recirculation

EGR Monitor – OBDII EGR Test

EGR TVV – Exhaust Gas Recirculation Thermal Vacuum Valve

EGRB – EGR Boost Sensor

EGRC – EGR Control Solenoid (Ford)

EGRC-BPT – EGR Control Back Pressure Transducer

EGRPS – EGR Valve Position Sensor (Mazda)

EGRT – Exhaust Gas Recirculation Temperature

EGRV – Exhaust Gas Recirculation Vent Solenoid

EGTS – Exhaust Gas Temperature Switch (replaced with EGRT)

EH – Electro-Hydraulic

EHC – Exhaust Heat Control vacuum solenoid or its circuit.

EI – Integrated Electronic Ignition System

EIC – Electronic Instrument Cluster.

EICV – Electronic Idle Control Valve

ELB – Electronic Lean Burn (Chrysler)

ELB (ELECTRONIC LEAN BURN) – An electronic ignition system designed to control ignition timing by firing an extremely lean air/fuel mixture.

ELC – Electronic Level Control

ELCD – Evaporative Loss Control Device

ELECTRIC FUEL PUMPS – Two electric fuel pump systems are used by Chrysler Motors vehicles: a high-pressure in-tank pump is used for certain high-pressure fuel injection systems, and a low-pressure in-tank pump is used for low-pressure fuel injection systems.

ELECTROMAGNETIC – A device which utilizes electronic and magnetic principles in its composition and operation.

ELECTROMECHANICAL – A device which utilizes electronic and mechanical principles in its composition and operation.

ELECTRONIC – Term used to describe an arrangement of conductors, semiconductors, and other components which accomplishes the control of system or devices through the use of electrical signals.

Electronic Control Unit – Processes input information to trigger ignition control module.

Electronic Feedback Carburetor – Utilizes an electronic signal, generated by an exhaust gas oxygen sensor to precisely control air/fuel mixture ratio in the carburetor.

ELECTRONIC FEEDBACK CARBURETOR (EFC) – Electronic Feedback Carburetor. Utilizes an electronic signal, generated by an exhaust gas oxygen sensor to precisely control air/fuel mixture ratio in the carburetor.

ELECTRONIC FUEL CONTROL – A computer control system was introduced on 1981 front wheel drive vehicles to control fuel and ignition systems through six sub-systems.

Electronic Fuel Injection – Electronic Fuel Injection. Computer controlled fuel injection system. On Ford EFI uses injectors in each intake port and CFI uses an injector in the throttle body.

ELECTRONIC SPARK ADVANCE (ESA) – An electronic ignition system, under control of the vehicle's on-board computer, which controls ignition timing and spark advance.

ELECTRONIC SPARK CONTROL – Used to retard spark advance if detonation occurs.

ELECTRONIC SPARK CONTROL (ESC) – A redesigned version of the ELB electronic ignition system.

ELECTRONIC SPARK TIMING – PCM controlled timing of the ignition spark.

EM – Engine Modification

EMB – Electromagnetic Brakes

EMF – Electromotive Force (voltage)

EMI – Electromagnetic Interference

EMR – Electronic Module Retard, controls spark retard.

EN – Generator (Alternator)

Enabling Criteria – Each Monitor is designed to test and monitor the operation of a specific part of the vehicle's emissions system (EGR system, oxygen sensor, catalytic converter, etc.). A specific set of "conditions" or "driving procedures" must be met before the computer can command a Monitor to run tests on its related system. These "conditions" are known as "Enabling Criteria." The requirements and procedures vary for each Monitor. Some Monitors only require the ignition key to be turned "On" for them to run and complete their diagnostic testing. Others may require a set of complex procedures, such as, starting the vehicle when cold, bringing it to operating temperature, and driving the vehicle under specific conditions before the Monitor can run and complete its diagnostic testing.

ENERGIZED – The condition of an electrical circuit having the electric current or source turned on.

ENGINE CONTROL MODULE – A microprocessor based device which contains electronic circuitry to control and monitor air/fuel and emission systems, and aid in diagnostics.

ENGINE CONTROL SYSTEM – A computer control system first used on 2.2L electronic throttle body fuel injected (TBI) vehicles to control fuel, ignition, and emission control systems through six sub-systems.

ENGINE RUNNING TEST MODE – The diagnostic mode used to read the output signals of specific sensors to the vehicle's on-board computer when the engine is idling. A SCAN Tool must be used during this test. The SCAN Tool displays the current operating condition of specific sensors and switches (Fault Codes are not generated during this test).

EOBD – European On Board Diagnostics

EOP – Engine Oil Pressure

EOS – Exhaust Oxygen Sensor

EOT – Engine Oil Temperature

EP – Exhaust Pressure

EPA – Environmental Protection Agency

EPC – Electronic Pressure Control

EPOS – EGR Valve Position Sensor (Ford)

EPROM – Erasable Programmable Read Only Memory.

EPT – EGR Pressure Transducer (replaced with PFE)

ER – Engine running, used on some Ford system tests.

ERS – Engine RPM Sensor.

ESA – Electronic Spark Advance (Chrysler)

ESC – Electronic Spark Control System (Ford)

ESD – Electrostatic Discharge

ESS – Electronic Spark Selection (Cadillac)

EST – Electronic Spark Timing

ETC – Electronic Temperature Control

ETP – EGR Pressure Transducer

ETR – Electronically Tuned Receiver

EVAP – Evaporative Emissions System

EVAP CP – Evaporative Canister Purge

EVAP CV – Evaporative Emissions System Canister Vent

EVIC – Electronic Vehicle Information Center

EVO – Electronic Vehicle Orifice

EVP – EGR Valve Position sensor or its circuit.

EVR – EGR Vacuum Regulator or its circuit.

EVRV – Electronic Vacuum Regulator Valve. Controls EGR vacuum.

EXH – Exhaust

EXHAUST GAS OXYGEN SENSOR – Sensor that changes its voltage output as exhaust gas oxygen content changes as compared to oxygen content of the atmosphere. The constantly changing electrical signal is used to control fuel mixture.

Exhaust Gas Recirculation – A procedure in which inert exhaust gases are recirculated to the combustion chamber to cool combustion temperatures and reduce nitrous oxides in exhaust.

EXHAUST GAS RECIRCULATION – Procedure where a small amount of exhaust gas is readmitted to combustion chamber to reduce peak combustion temperatures, thus reducing NOx.

EXHAUST HEAT CONTROL VALVE – A valve which routes hot exhaust gases to the intake manifold heat riser during cold engine operation. The valve is controlled either by a thermostat or by engine vacuum.

F.I. – Fuel Injection

F4WD – Full Time Four Wheel Drive

FAIL SAFE – or Fail Soft: any attempt by a computer to compensate for a fault or lost signal, usually by substituting fixed replacement valves.

FAN – Cooling Fan (Low or High Speed)

FAULT CODES – A series of two-digit numbers, stored in the vehicle's on-board computer, which represent the results of On-Board Diagnostics or Vehicle Diagnostics. The computer transmits this information, via the Diagnostic Connector, as a series of pulses read either on a SCAN Tool, or as flashes of the "Power Loss/Check Engine" light on the vehicle's instrument panel.

FBC – Feedback Carburetor

FBCA – Feedback Carburetor Actuator (Ford)

FC – Fan Control

FCA – Fuel Control Assembly (Chrysler)

FCS – Fuel Control Solenoid (Ford)

FCS (FEEDBACK CONTROL SOLENOID) – Controls the introduction of filtered fresh air into the idle and main system bleed passages of the carburetor.

FCS (FUEL CONTROL SOLENOID) – Device which controls the carburetor air/fuel ratio. The FCS can be either a pulsating duty-cycle solenoid which bleeds air into the main and idle fuel systems, or a combined duty-cycle solenoid and vacuum regulator which controls fuel flow in the main fuel system and bleeds air into the idle fuel system.

FDBK – Feedback

FDC – Fuel Deceleration Valve (Ford)

FDV – Fuel Decel Valve (Ford)

FEED CIRCUIT – The power supply or hot wire.

FEEDBACK CARBURETOR (FBC) – System of fuel control employing a computer controlled solenoid that varies the carburetors air/fuel mixture.

FEEDBACK CARBURETOR ACTUATOR – Computer controlled stepper motor used on Ford feedback carburetors, that varies air/fuel mixture.

FEEPROM – Flash Electronically Erasable Programmable Read Only Memory

FEPROM – Flash Erasable Programmable Read Only Memory

FERROMAGNETIC MATERIAL – Any material with high magnetic permeability and high residual magnetism.

FF – Flexible Fuel

FI – Fuel Injector

FIC – Fast Idle Control

FICD – Fast Idle Control Device

Filtered Tachometer Output – An output from Ford DIS TFI IV module which provides a filtered ignition signal to the processor in order to control dwell.

FIPL – Fuel Injection Pump Lever

FLC – Fluid Lock-up Converter (Ford)

FLS – Fluid Level Sensor (GM)

FLUX LINES – The lines of magnetic force (also referred to as Maxwells).

FM – Fan Motor Program in PCM

FMEM – Failure Mode Effects Management. Sometimes referred to limp-in mode.

FMVSS – Federal Motor Vehicle Safety Standards

FOM – Fix Operating Mode (Limp Mode)

FP – Fuel Pump Relay (Ford)

FP – Fuel Pump

FPM – Fuel Pump Monitor (in PCM)

FPRC – Fuel Pump Regulator Control

FRC – Forced

Freeze Frame – A digital representation of engine and/or emissions system conditions present when a fault code was recorded.

FREQUENCY – The number of cycles-per-second (complete alternations) of an alternating current.

FRP – Fuel Rail Pressure

FRT – Fuel Rail Temperature

FRZ – Freeze Frame

FT – Fuel Trim

FTL – Fuel Tank Level Sensor

FTO – Filtered Tachometer Output

FTP – Fuel Tank Pressure

FTT – Fuel Tank Temperature

FUEL FILTER – A device installed in the pressure line to prevent foreign particles from entering the remainder of the fuel system (particularly the injectors).

FUEL INJECTOR – An assembly which receives a metered charge of fuel from another source, and is actuated by an engine mechanism to inject the charge of fuel into the combustion chamber at the proper time.

FUEL PRESSURE (INLET) LINE – The pressurized line, usually constructed of rubber, metal or plastic, which carries the fuel supply from the fuel tank to the fuel pump and the fuel injectors.

FUEL PRESSURE REGULATOR – A device which maintains a controlled fuel pressure at the fuel injector or a controlled differential pressure across the fuel injector.

FUEL PUMP – A device (electrical or mechanical) which provides a specified fuel flow at the required system pressure.

FUEL PUMP INLET SCREEN FILTER – A screen-type filter mounted on the in-tank fuel pump which protects the pump inlet drawing excess dirt and foreign particles.

FUEL PUMP RELAY – Provides power to the electric fuel pump in TBI/EFI systems. The relay is either controlled by, or is an integral part of, the ASD relay.

FUEL RAIL – A fuel manifold line which carries and distributes the fuel to the individual injectors (used with Multi-port Fuel Injection systems).

FUEL RETURN LINE – The line which carries unused fuel from the fuel rail or throttle body back to the fuel tank.

FUEL RICH, LEAN – An evaluation of the air/fuel ratio based on the input received from the oxygen sensor. An air/fuel mixture with an excessive amount of oxygen is referred to as "lean"; an air/fuel mixture with an insufficient amount of oxygen is referred to as "rich".

FUEL SYSTEM INERTIA SWITCH – A device used in most Ford vehicles which acts as a circuit breaker for the fuel system's electrical components (refer to your vehicle's service manual for location).

FUEL SYSTEM TEST PORT – A test port or opening incororated in the fuel rail or throttle body specifically designed to provide easy access to test and clean the fuel system.

FUEL TANK – A holding apparatus, usually constructed of metal or plastic, which stores the vehicle's fuel supply.

FUEL-VACUUM SEPARATOR – A filtering device which protects the vacuum delay and distributor vacuum controls by removing hydrocarbons from carburetor-ported vacuum.

FUSE – A mechanical device which contains a soft piece of metal which opens (melts) and breaks the circuit during high current (overload) conditions.

FUSIBLE LINK – A device which protects a circuit from damage if a short to ground occurs, or if the polarity of the battery (or charger) is reversed.

FWD – Front Wheel Drive

g/sec – Grams per Second

GA – Gage

GCM – Governor Control Module

GCW – Gross Combination Weight

GDC – Fuel Data Center

GDI – Gasoline Direct Injection

GEM – Generic Electronic Module

GEN – Generator (Alternator)

GENERATE – To produce electricity by the process of electromagnetic induction.

Generic Code – A DTC that applies to all OBD 2 compliant vehicles.

GND – Electrical Ground Connection

GOOSE – Brief Throttle Open/Close

GPM – Grams Per Mile

GPS – Governor Pressure Sensor

GROUND (OR GND) – In automotive applications, the common line leading to the negative side of the battery.

GROUND-SIDE SWITCH – A switch located in the ground side of a circuit instead of the hot wire.

GST – Generic Scan Tool

GVW – Gross Vehicle Weight

H – Hydrogen

H/CMPR – High Compression

H2O – Water

HAC – High Altitude Compensator

HAIS – Heated Air Intake System (Chrysler)

HALL EFFECT – Process where current is passed through a small slice of semiconductor material at the same time as a magnetic field to produce a small voltage in the semiconductor.

HARD FAULT – Fault present during current engine operating cycle. Opposite of an intermittent fault which does not stay present.

HARD FAULT CODE – A circuit or component failure that reappears after codes have been cleared and the system has been retested.

HBV – Heater Blower Voltage

HC – Hydrocarbons

HCDS – High Clutch Drum Speed

HCV – Exhaust Heat Control Valve (Ford)

HCV – Hydrocarbon (Ford)

HD – Heavy Duty

HDC – Heavy Duty Cooling

HDR-CKP – High Data Rate CKP Sensor

HEATED OXYGEN SENSOR (HO2S) – The heated oxygen sensor monitors the oxygen content of the vehicle's exhaust gases, and generates a voltage signal (representing the air/fuel ratio) used by the vehicle's on-board computer for fuel control. The heated sensor contains a heating element to keep the sensor at consistent temperature, allowing the system to enter closed loop earlier and maintain closed loop operation with the engine at idle speed.

Heater Blower Voltage – Heater Blower Voltage input to EEC-IV processor reflecting heater blower voltage demand.

HEDF – High-speed Electro-Drive Fan relay or its circuit.

HEGO – Heated Exhaust Gas Oxygen Sensor

HEI – High Energy Ignition (GM)

HFC – High (speed) Fan Control

HFP – High Fuel Pump (Relay) Control

Hg (MERCURY) – A material used as a calibration standard for vacuum measurement.

HIC – Hot-Idle Compensator (Ford)

HIGH TENSION SECONDARY VOLTAGE – Voltage which enables current to jump the spark plug gap. This voltage is caused by the collapse of the magnetic field around the coil secondary windings.

HIGH-RESISTANCE SHORT – A short circuit which draws a slow current.

HLOS – Hardware Limited Operation System

HO – High Output

HO2S – Heated Oxygen Sensor

HO2S-1-1 – Bank One Sensor One Signal

HO2S-1-2 – Bank One Sensor Two Signal

HO2S-1-3 – Bank One Sensor Three Signal

HO2S-2-1 – Bank Two Sensor One Signal

HO2S-2-2 – Bank Two Sensor Two Signal

hp – Horsepower

HPC – High Pressure Cutoff

HPL – High Pressure Liquid

HPS – High Performance System

HPV – High Pressure Vapor

HSC – High Swirl Combustion

HT – High Tension

HUD – Heads Up Display

HVAC – Heater Ventilation and Air Conditioning

HVACM – Heater-Vent-Air Conditioning Module

HVS – High Voltage Switch

Hz – Hertz

I/M – Inspection and Maintenance

I/M Readiness – An indication of whether or not a vehicle's emissions-related system are operating properly and are ready for Inspection and Maintenance testing.

I/M Test / Emissions Test / Smog Check – A functional test of a vehicle to determine if tailpipe emissions are within Federal/State/Local requirements.

I/O – Input / Output

I/P – Instrument Panel

IA – Intake Air

IAC – Idle Air Control (motor or solenoid)

IACV – Idle Air Control Valve

IAS – Inlet Air Solenoid valve or its circuit.

IAT – Intake air temperature sensor, performs same function as MAT sensor.

IBP – Integral Back Pressure

IC – Ignition Control

IC – Integrated Circuit

ICM – Ignition Control Module

ICM – Integrated Control Module.

ICP – Injection Control Pressure

ICS – Idle Control Solenoid (GM)

ID – Inside Diameter

IDI – Integrated Direct Ignition

IDL – Idle Position Switch

Idle Speed Actuator – Extends or retracts to control engine idle speed and to set throttle stop angle during deceleration.

Idle Speed Control – Idle Speed Control, either computer control motor, air bypass valve, or any device used to control idle rpm.

IDLE SPEED STEPPER (ISS) MOTOR – The ISS motor (used on some Jeep engines) controls airflow inside the throttle body bypass passage to control idle speed. The ISS motor operates under control of the vehicle's on-board computer.

IDLE TRACKING SWITCH – An input device that sends a signal to the computer to indicate a closed throttle condition.

IDM – Ignition Diagnostic Monitor

IDM – Injector Driver Module

IFI – Indirect Fuel Injection

IFS – Inertia Fuel Switch

IGN – Ignition

IGN ADV – Ignition Advance

IGN GND – Ignition Ground

Ignition Diagnostic Monitor – Continuous monitor of ignition input to EEC-IV processor used to detect intermittent ignition faults.

ILC – Idle Load Compensator

IMA – Idle Mixture Adjuster

IMPEDANCE – The total opposition of a circuit to the flow of alternating current, measured in ohms (includes resistance and reactance).

IMRC – Intake Manifold Runner Control

IMS – Ignition Module Signal

IMS – Inferred Mileage Sensor (Ford)

IMT – Intake Manifold Timing

INDUCTION – The process of magnetizing and object, or of inducing a voltage in an object by placing it within a magnetic field.

INJ 1 to INJ 10 – Fuel Injectors 1 to 10

INJECTOR – A fuel injection system electrical solenoid which, when energized, allows fuel flow into the intake manifold where it is mixed with air for combustion.

INPUTS – Information, in the form of a voltage or current, from a device external to the vehicle's on-board computer (switch, sensor, etc.) which assists the computer in monitoring and maintaining engine performance.

INSULATOR – Any material which will not conduct current. Insulators are commonly used to support or isolate conductors in an electrical/electronic circuit.

INT – Integrator (replaced with ST FUEL TRIM)

INTERMITTENT – Occuring infrequently (not continuously) and usually on an irregular basis. In electrical circuits, it refers to an occasional open, short, or ground.

INTERMITTENT FAULT – Fault which occurred during a previous engine operating cycle. Intermittent fault may have set a fault code which is still present in PCM memory.

IPC – Instrument Panel Cluster

IPR – Injector Pressure Regulator

IRCM – Integrated Relay Control Module, used on some Ford systems.

ISA – Idle Speed Actuator

ISC – Idle Speed Control

ISO – International Standard of Organization

ISS – Input Shaft Speed

ITA – Ignition Timing Adjustment

ITCS – Ignition Timing Control System (Honda)

ITS – Idle Tracking Switch

IVS – Idle Validation Switch

IVSC – Integrated Vehicle Speed Control

IVV – Idle Vacuum Valve (Ford)

JAS – Jet Air System (Mitsubishi)

JSV – Jet Mixture Solenoid Valve

KAM – Keep Alive Memory

KAPWR – Direct Battery Power, used to power KAM circuit of the processor.

KD – Kickdown

KDLH – Kickdown Low Hold

Keep Alive Memory – Battery power memory locations in computer used to store failure codes and some diagnostic parameters.

Kg/cm2 – Kilograms/ Cubic Centimeters

kHz – Kilohertz

Km – Kilometers

KNOCK SENSOR (KS) – Input device that responds to spark knock, caused by over advanced ignition timing.

KOEC – Key On, Engine Cranking

KOEO – Key On, Engine Off

KOER – Key On, Engine Running

KPA – Kilopascal

KS – Knock Sensor

KSM – Knock Sensor Module

L – Liters

L4 – Four Cylinder Inline Engine

LAB OSCILLOSCOPE – An electronic device used to analyze voltages. The oscilloscope produces a picture of the voltage waveform on a CRT screen.

LAMBSE – Short Term Fuel Trim

LCD – Liquid Crystal Display

LEAN MIXTURE – Air/fuel mixture that has excessive oxygen left after all fuel in combustion chamber has burned, 1 part fuel to 15 or more parts air.

LED – Light Emitting Diode

LFC – Low Fan Control

LFP – Low Speed Fuel Pump Control

LHD – Left Hand Drive

LIGHT-EMITTING DIODE (LED) – A positive/negative junction of crystal which produces light when forward bias current is applied.

LIMP-IN MODE – A condition where the vehicle's on-board computer has detected a faulty or failed input device (switch, sensor, etc) and has substituted a known value for the failed input. When this condition occurs, driveability is greatly affected; but will allow the operator to get the vehicle to a service facility.

LINEAR – A mathematically expressed relationship, the graphical representation of which is a straight line.

LOAD – Calculated Load Value

LOC – Light Off Catalyst

LOCK UP TORQUE CONVERTER – Converter with internal mechanism that locks turbine to impeller when engaged.

LOCK-UP TORQUE CONVERTER SOLENOID – A transaxle-mounted solenoid, operating under control of the vehicle's on-board computer, which engages the torque converter to directly connect the engine to the transaxle.

LOGIC MODULE – A microprocessor (located in the vehicle's on board computer) which receives inputs from the vehicle's engine control system sensors, and generates the output signals to control engine operation an an optimum balance between engine performance, vehicle emissions and fuel economy.

LOGIC PROBE – A device used to verify operation of a logic (on/off) circuit.

Long Term Fuel Trim – A program in the vehicle's computer designed to add or subtract fuel from the vehicle to compensate for operating conditions that vary from the ideal A/F ratio (long term).

LONGFT – Long Term Fuel Trim

LOOP – Engine Operating Loop Status

LOS – Limited Operating Strategy

LPG – Liquid Petroleum Gas

LSS – Linear Shift Solenoid

LTFT – Long Term Fuel Trim

LTS – Low Coolant Switch

LUS – Lock-Up Solenoid

LV8 – Load Variable

LWB – Long Wheel Base

M/C – Mixture control or mixture control solenoid.

M/T – Manual Transmission

MAF – Mass Air Flow Sensor

MAF RTN – Mass Airflow Sensor Ground

MAGNETIC FIELD – The portion of space near a magnetic body in which magnetic lines of force exist.

MAGNETIC PICK-UP COIL – Coil used in electronic distributor ignition systems to determine when to switch off the coil secondary.

MAGNETIC RELUCTANCE – The opposition of a magnetic substance to the flow of magnetic flux through it.

MALFUNCTION – A problem which causes a system to operate incorrectly. Typical malfunctions are wiring harness opens or shorts, failed sensors, or circuit components.

MALFUNCTION INDICATOR LIGHT (MIL) – Generic term for various warning lamps used to indicate malfunctions in the vehicle's engine management system (on-board computer and associated input/output devices).

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR – A sensor which sends a varying frequency signal (based on manifold vacuum and manifold pressure) to the vehicle's on-board computer for calculation of barometric pressure.

Manufacturer Specific Code – A DTC that applies only to OBD 2 compliant vehicles made by a specific manufacturer.

MAP – Manifold Absolute Pressure sensor or its circuit.

MAS – Mixture Adjust Screw

Mass Air Flow Sensor – Used to measure amount of airflow through the throttle body.

MAT – Manifold Air Temperature.

MC – Mixture Control

MCS – Mixture Control Solenoid (GM)

MCT – Manifold Charge Temperature Sensor (Ford)

MCU – Microprocessor Control Unit (Ford)

MCV – Manifold Control Valve (Ford)

MDP – Manifold Differential Pressure

MECS – Mazda Electronic Control System

MEMCAL – Memory Calibration

MERCURY (Hg) – A material used as a calibration standard for vacuum measurement.

MFI – Multi-port Fuel Injection.

MIC – Mechanical Instrument Cluster

MICROPROCESSOR – A small processor located in the vehicle's computer.

MICROPROCESSOR CONTROL UNIT (MCU) – The controlling computer, used on early Ford feedback carburetor systems and all 5.8L feedback carburetor equipped Fords.

MIL – Malfunction Indicator Lamp (also referred to as "Check Engine" light

MISAR – Microprocessed Sensing and Automatic Regulation (GM)

MIXTURE CONTROL SOLENOID – Device installed on carburetor, that regulates the air/fuel ratio.

MLP – Manual (shift) Lever Position sensor or its circuit.

MLUS – Modulated Lock Up Solenoid or its Control Circuit (Ford)

MLVLPS – Manual Valve Lever Position

MODE – A specific state or condition of operation.

MODULE – A mechanical, electrical or electromechanical arrangement of components intended to perform a specific task (such as ignition). Modules are usually designed to allow easy removal and replacement.

Monitor – Monitors are "diagnostic routines" programmed into the PCM. The PCM utilizes these programs to run diagnostic tests, and to monitor operation of the vehicle's emissions-related components or systems to ensure they are operating correctly and within the vehicle's manufacturer specifications. Currently, up to eleven Monitors are used in OBD 2 systems. Additional Monitors will be added as the OBD 2 system is further developed. Not all vehicles support all eleven Monitors.

Monitor Has/Has Not Run – The terms "Monitor has run" or "Monitor has not run" are used throughout this manual. "Monitor has run," means the PCM has commanded a particular Monitor to perform the required diagnostic testing on a system to ensure the system is operating correctly (within factory specifications). The term "Monitor has not run" means the PCM has not yet commanded a particular Monitor to perform diagnostic testing on its associated part of the emissions system.

MPFI – Multi-Port Fuel Injection

MPG – Miles Per Gallon

MPH – Miles Per Hour

MPI – Multi Port Injection

mS or ms – Millisecond

MSFF – Miles Since First Fail

MSLF – Miles Since Last Fail

MST – Manifold Surface Temperature

MT – Manual Transmission

MTV – Manifold Tune Valve

MULTI-PORT FUEL INJECTION – Individual injectors for each cylinder mounted in intake manifold. Injectors are pulsed in groups rather than individually.

mV or mv – Milivolt

MVLPS – Manual Valve Lever Position

MVZ – Manifold Vacuum Zone

N – Nitrogen

N.C. – Normally Closed Position

N.O. – Normally Open Position

N/MIL – A Code Set Without a MIL Request

N/V – Input Shaft Speed to Vehicle Speed

NDIR – Non Dispersive Infrared

NDS – Neutral Drive Switch.

NEUTRAL/SAFETY SWITCH – A switch which signals the vehicle's on-board computer that the automatic transaxle is in neutral. The computer uses this signal for spark timing control, torque converter clutch operation, and idle speed control.

NGS – Neutral Gear Switch or its circuit.

NGV – Natural Gas Vehicles

Nm – Newton Meters

NON-VOLATILE MEMORY – Memory retained in block learn cells (not affected by turning the ignition ON or OFF).

NOx – Oxides of Nitrogen

NPS – Neutral Pressure Switch or its circuit.

NTC – Negative Temperature Coefficient

NVRAM – Non Volatile Random Access Memory

O2 – Oxygen

O2 (OXYGEN) SENSOR – The oxygen sensor monitors the oxygen content of the vehicle's exhaust gases and generates a voltage signal (representative of the air/fuel ratio) used by the vehicle's on-board computer for fuel control.

O2S-11 – Oxygen Sensor Signal (Bank 1)

O2S-21 – Oxygen Sensor Signal (Bank 2)

OASIS – Ford Motor Company Online Automotive Service Information System

OBD (ON-BOARD DIAGNOSTICS) – Refers to the self-testing ability of the vehicle's on-board computer which allows the computer to verify its own operational ability.

OBD (ON-BOARD DIAGNOSTICS) – Refers to the self-testing ability of the vehicle's on-board computer which allows the computer to verify its own operational ability.

OBD 1 – On-Board Diagnostics Version 1 (also referred to as "OBD I")

OBD 2 – On-Board Diagnostics Version 2 (also referred to as "OBD II")

OBD 2 Drive Cycle – An OBD 2 Drive Cycle is an extended set of driving procedures that takes into consideration the various types of driving conditions encountered in real life. These conditions may include starting the vehicle when it is cold, driving the vehicle at a steady speed (cruising), accelerating, etc. An OBD 2 Drive Cycle begins when the ignition key is turned "On" (when cold) and ends when the vehicle has been driven in such a way as to have all the "Enabling Criteria" met for all its applicable Monitors. Only those trips that provide the Enabling Criteria for all Monitors applicable to the vehicle to run and complete their individual diagnostic tests qualify as an OBD 2 Drive Cycle. OBD 2 Drive Cycle requirements vary from one model of vehicle to another. Vehicle manufacturers set these procedures. Consult your vehicle's service manual for OBD 2 Drive Cycle procedures. Do not confuse a "Trip" Drive Cycle with an OBD 2 Drive Cycle. A "Trip" Drive Cycle provides the "Enabling Criteria" for one specific Monitor to run and complete its diagnostic testing. An OBD 2 Drive Cycle must meet the "Enabling Criteria" for all Monitors on a particular vehicle to run and complete their diagnostic testing.

OBD I – On Board Diagnostics Version I

OBD II – On Board Diagnostics Version II

OBD STAT – On Board Diagnostic System Status

OC – Oxidation Catalytic Converter

OCC – Output Circuit Check (Ford)

OCIL – Overdrive Cancel Indicator Lamp

OCS – Overdrive Cancel Switch

OCT ADJ – Octane Adjust device which modifies ignition spark.

OD – Outside Diameter

OD – Overdrive

ODM – Output Device Monitor

ODS – Overdrive Drum Speed

OE – Original Equipment

OEM – Original Equipment Manufacturer

OHC – Overhead Cam Engine

OHM – Unit of electrical resistance. A circuit has one ohm of resistance when one volt applied to it produces a current of one ampere.

OHV – Over Head Valve

OL – Open Loop

On-Board Computer – The central processing unit in the vehicle's computer control system.

OPEN CIRCUIT – A circuit which does not provide a complete path for the flow of current.

ORC – Oxidation Reduction Converter

OS – Oxygen Sensor

OSAC – Orifice Spark Advance Control (Chrysler)

OSC – Output State Check (Ford)

OSCILLOSCOPE – A test instrument used to analyze an electronic circuit. The oscilloscope displays circuit activity as a waveform on a CRT screen.

OSM – Output State Monitor

OSS – Output Speed Shaft

OTIS – Overhead Travel Information System

OVCV – Outer Vent Control Valve

P/B – Power Brakes

P/E – Power Enrichment

P/N – Part Number

P/S – Power Steering

PA – Pressure Air (Honda)

PAFS – Pulse Air Feeder System (Chrysler)

PAIR – Pulsed Secondary Air Injection

PARALLEL CIRCUIT – A circuit in which there are two or more paths for current flow.

PAS – passive Anti-Theft System

PAS – Power Assisted Steering

PASS – Personalized Automotive Security System

PC – Pressure Control

PCB – Printed Circuit Board

PCI – Programmable Communications Interface

PCM – Powertrain Control Module

PCM (POWERTRAIN CONTROL MODULE ) – Generic term used to refer to the arrangement controllers/computers which control the engine management system, emissions systems, and the shift operations of automatic transmissions. This term is Federally mandated to standardize the terminology of engine management computers (beginning in the 1993 model year).

PCS – Pressure Control Solenoid

PCV – Positive Crankcase Ventilation

PCV (POSITIVE CRANKCASE VENTILATION) – A system which vents vapors from the crankcase into the engine intake system where they are burned in the engine cylinders rather than being discharged in the exhaust gases.

PECV – Power Enrichment Control Valve

Pending Code – A code recorded on the "first trip" for a "two-trip" code. If the fault that caused the code to be set is not detected on the second trip, the code is automatically erased.

PF – Purge Flow Sensor

PFE – Pressure Feedback EGR sensor or its circuit.

PFI – Port Fuel Injection

PFI/MFI – General abbreviation for Port or Multi-port Fuel Injection.

PGM-FI – Programmed Gas Management Fuel Injection (Honda)

PID – Parameter Identification

PID SUP – Parameter Identification Supported

PIP – Profile Ignition Pickup.

PIV – Peak Inverse Voltage

PKE – Passive Keyless Entry

PMD – Pump Mounted Driver

PNP – Par Neutral Position

PORTED VACUUM SWITCH – Temperature actuated switch that changes vacuum connections when the coolant temperature changes.

POT – Potentiometer

POTENTIOMETER (POT) – A variable resistor with three connections. The two ends of the resistive element each constitute one connection. The third connection (called the wiper) moves physically up and down the resistive element to vary the resistance of the device.

POWER LOSS LAMP – Term for the instrument panel-mounted lamp on early Chrysler vehicles (functions the same as the Check Engine Light).

POWER MODULE – A microprocessor which delivers commands from the on-board computer's Logic Module to the various actuators in the vehicle's engine control system.

Power Steering Pressure Switch – Signal is used by computer to compensate for power steering loads.

POWERTRAIN CONTROL MODULE (PCM) – Same as ECM, but also controls electronically controlled automatic transmission. The PCM is the OBD 2 accepted term for the vehicle's "on-board computer." In addition to controlling the engine management and emissions systems, the PCM also participates in controlling the powertrain (transmission) operation. Most PCMs also have the ability to communicate with other computers on the vehicle (ABS, ride control, body, etc.).

PPM – Parts Per Minute

PPS – Ported Pressure Switch (Ford)

PR – Pressure Relief

PRC – Pressure Regulator Control

PRESSURE REGULATOR – A device which controls the pressure of the fuel delivered to the fuel injector(s).

PRIMARY WINDING – The low voltage winding of the ignition coil which is electronically connected to its secondary winding only by the magnetic field they share. When the primary winding is connected across the supply voltage, a potential current flows through it, building a magnetic field around itself, and inducing a voltage in the secondary winding. When the primary winding is disconnected, the cease in current through the primary winding again induces a voltage in the secondary winding which provides current to the spark plugs to ignite the air/fuel mixture.

PRNDL – Switch

PROFILE IGNITION PICKUP – A Hall effect vane switch that furnishes crankshaft position data to the EEC-IV processor.

PROM – Programmable Read Only Memory.

PS – Power Steering

PSA – Pressure Switch Assembly

PSC – Power Steering Control

PSI – Pounds Per Square Inch

PSOM – Programmable Speedometer Odometer Module

PSOV – Purge Shut Off Valve (Ford)

PSP – Power Steering Pressure

PSPS – Power Steering Pressure Switch

PTC – Positive Temperature Coefficient Resistor

PTO – Power Take Off (4WD Option)

PTOX – Periodic Trap Oxidizer

PTU – Part Throttle Unlock

PULSE – An abrupt change in a voltage either (positive or negative).

PVA – Ported Vacuum Advance

PVS – Ported Vacuum Switch

PWM – Pulse Width Modulation

PWR GND – Power Ground for PCM

QDM – Quad Driver Module

QUICK TEST – A functional diagnostic test for Ford EEC-IV system, consisting of test hookup, key on engine off, engine running and continuous self test models.

RABS – Rear Antilock Brake System

RAM – Random Access Memory

RAP – Retained Access Power

RAP – Retained Accessory Power.

RATIO – The relationship in quantity, amount or size between one value and another.

RECAL – Calibration Adjustment

REDOX – Reduction Oxidation Converter

REF – Reference

REFERENCE VOLTAGE (VREF) – Regulated voltage provided by the vehicle's computer to some vehicle sensors.

RELAY – Switching device operated by a low current circuit, which controls opening and closing of another higher current circuit.

RELIEF VALVE – Pressure limiting valve located in exhaust chamber of thermactor air pump. Relieves part of exhaust airflow if pressure exceeds a calibrated value.

RESISTANCE – The property of a device or circuit which causes it to oppose the movement of current through it. The unit of electrical resistance is the ohm.

RESISTOR – An electronic component (most commonly made of carbon) which restricts the flow of current.

REST PRESSURE – Fuel pressure maintained within the fuel system after the engine is turned off.

RFI – Radio Frequency Interference

RHD – Right Hand Drive

RICH MIXTURE – Air/fuel mixture that has more fuel than can burn completely, 1 part fuel to 14 or less parts air.

RKE – Remote Keyless Entry

RM – Relay Module

ROM – Read Only Memory

RON – Rated Octane Number

RPM – Revolutions Per Minute

RRS – Variable Reluctance Sensor

RTD – Real Time Dampening

RTN – Dedicated Sensor Ground Circuit

RTV – Room Temperature Vulcanizing

RVP – Reid Vapor Pressure

RWAL – Rear Wheel Anti-Lock

RWD – Rear Wheel Drive

S4WD – Selectable Four Wheel Drive

SAE – Viscosity Grade

SA-FV – Separator Assembly Fuel/Vacuum

SAVM – Spark Advance Vacuum Modulator

SAW – Spark Advance Word, and also Spark Angle Word.

SBDS – Service Bay Diagnostic System

SBEC – Single Board Engine Controller (replaced with PCM0

SBS – Boost Solenoid (Ford)

SBT – Serial Bus Traveler

SC – Super Charged

SCAP – Silicone Capacitance Absolute Pressure Sensor (Ford)

SCB – Supercharger Bypass

SCC – Spark Control Computer.

SCP – Standard Corporate Protocol

SDI – Saab Direct Ignition

SDM – Sensing Diagnostic Module

SDV – Spark Deceleration Valve

SDV – Spark Delay Valve

SECONDARY WINDING – The winding of the ignition coil which supplies high tension current to the spark plugs. The secondary winding is activated by the collapsing magnetic field of the primary winding.

SEFI – Sequential Electronic Fuel Injection

Self Test Input – (Ford) Circuit in EEC or MCU systems. Used to place computer into testing mode.

Self Test Output – Self Test Output (Ford) circuit in EEC or MCU systems. Used by computer to send testing and fault codes to tester.

SELF-TEST – One of 3 subsets of Ford EEC-IV quick test modes.

SENSOR – Any component which can detect and relay information relating to the operational status of a component or system.

SENSOR TEST MODE – The diagnostic mode used to check the output signal of specific sensor with the engine off. Specific codes are entered on the SCAN tool to select the desired for test. The output of this mode is the actual output of the selected sensor (temperature, voltage, speed, etc.).

SEO – Special Equipment Option

Sequential Electronic Fuel Injection – Injectors located in intake ports that inject fuel triggered by ignition timing.

Sequential Fuel Injection – Type of MFI with injectors pulsed individually based on engine firing order.

SERIES CIRCUIT – A circuit in which each component is attached, one end to the other, providing only one path for current flow.

SERVICE REMINDER INDICATOR (SRI) – Indicator light which informs the driver that the vehicle is due for service (called the Maintenance Reminder Light in pre-1993 vehicles).

SES – Service Engine Soon (replaced with MIL)

SFI – Sequential Fuel Injection

SHED – Sealed Housing Evaporative Determination System

Shift Indicator Lamp – Indicates to driver optimum time to shift gears.

SHO – Super High Output Engine

SHORT – A generally unintended (accidental) connection in an electrical circuit which shortens the electrical path, and, depending on its location in the circuit, causes increased current to flow.

SHRT FT – Short Term Fuel Trim

SHRTFT1 – Short Term Fuel Trim Bank 1

SIG RTN – Signal Return (sensor ground)

SIL – Shift Indicator Lamp

SINGLE BOARD ENGINE CONTROLLER – This computer system is used on some post-1989 3.0L engine-equipped Chrysler Motors vehicles. The Logic Module and Power Module are combined on a single printed circuit board.

SINGLE MODULE ENGINE CONTROLLER (SMEC) – This computer system is used on some post-1987 Chrysler Motors vehicles. The Logic Module and Power Module are housed in a common enclosure.

SIPS – Side Impact Protections System

SIR – Supplemental Inflatable Restraint (SIR) system; air bag.

SIS – Solenoid Idle Stop

SMEC – Single Module Engine Controller (replaced with PCM)

SMPI – Sequential Multiport Fuel Injection (Chrysler)

SO2 – Sulfur Dioxide

SOFT FAULT CODE – A circuit or component failure, recorded by the vehicle's on board computer, that does not reappear after codes have been cleared and the system retested.

SOHC – Single Overhead Cam

SOLENOID – Wire coil with a movable core which changes position by means of electromagnetism when current flows through the coil.

SOLID STATE – Refers to circuits which use transistors, integrated circuits, and/or other semi-conductors. Any electronic circuit which does not use vacuum tubes can be considered solid state.

SPARK ADVANCE – Causing spark to occur earlier.

Spark Output Signal – Spark output signal from EEC-IV processor to TFI-IV module, used to control amount of timing retard.

SPARK RETARD – Causing less spark advance to be added, resulting in a spark which is introduced later.

SPARK RETARD SOLENOID – Output device that receives an output signal from Ford MCU system to bleed distributor's vacuum advance when spark knock occurs.

SPD – Speed

SPEED (DISTANCE SENSOR) – Sensor is mounted at the transaxle tailshaft housing which transmits a signal representing vehicle speed to the vehicle's on-board computer.

SPFI – Single Point Fuel Injection (throttle body)

SPI – Serial Peripheral Interface

SPL – Smoke Puff Limiter

SPOUT – Spark Output Signal

SPS – Service Programming System

SRC – Selective Ride Control

SRDV – Spark Retard Delay Valve

SRI – Service Reminder Indicator

SRS – Spark Retard Solenoid

SRS – Supplemental Restraint System (air bag)

SRT – System Readiness Test

SS – Speed Sensor (Honda)

SS1, SS2,etc. – Shift Solenoid 1, 2, etc.

SSI – Solid State Ignition system.

ST – Scan Tool

STAR – Self Test Automatic Readout

STFT – Short Term Fuel Trim, is a program in the vehicle's computer designed to add or subtract fuel from the vehicle to compensate for operating conditions that vary from the ideal A/F ratio. The vehicle uses this program to make minor fuel adjustments (fine tune) on a short-term basis.

STI – Self Test Input

STO – Self Test Output

STOICHIOMETRY – In automotive applications, the air/fuel ratio resulting in optimum combustion; it enables exactly all of the fuel to burn using exactly all of the available oxygen.

STS – Service Throttle System (lamp)

SUSP – Suspension System Module

SVV – Solenoid Vent Valve (Ford)

SWB – Short Wheel Base

T.V. – Throttle Valve.

TA – Temperature Air (Honda)

TAB – Thermactor Air Bypass

TAC – Thermostatic Air Cleaner (GM)

TAC – Throttle Actuator Control

TACH – Tachometer

TACH INPUT – Engine rpm signal sent to computer from ignition coil primary circuit.

TAD – Thermactor Air Diverter solenoid.

TAP – Transmission Adaptive Pressure

TAV – Temperature Actuated Vacuum

TBI – Throttle Body Injection

TBI (THROTTLE BODY INJECTION) – Any one of several fuel injection systems which have the fuel injector(s) mounted in a centrally-located throttle body, rather than close to an intake port.

TC – Turbocharger

TCA – Thermostat Controlled Air Cleaner

TCC – Torque Converter Clutch

TCCP – Torque Converter Clutch Pressure

TCCS – Toyota Computer Controlled System

TCIL – Transmission Control Indicator Lamp

TCM – Transmission Control Module

TCP – Temperature Compensated Accelerator Pump (Ford)

TCP – Temperature Compensating Pump.

TCP – Torque Charger

TCS – Traction Control Switch

TCS – Transmission Control Switch

TCS – Transmission Controlled Spark (GM)

TD – Turbo Diesel

TDC – Top Dead Center

TDI – Turbo Direct Injection

TE – Thermal Expansion

TFI – Thick Film Ignition module. Controls coil and ignition operation on most Ford vehicles.

TFP – Throttle Fluid Pressure

TFP – Transmission Fluid Pressure

TFT – Transmission Fluid Temperature

THERMACTOR AIR BYPASS SOLENOID – Solenoid switches engine manifold vacuum. Vacuum reacts on thermactor bypass valve to bypass thermactor air to the atmosphere. Used on Ford MCU feedback carburetor system.

THERMACTOR AIR CONTROL VALVE – Combines function of a normally closed air bypass valve and an air diverter valve in one integral valve.

THERMACTOR AIR DIVERTER SOLENOID – Solenoid switches engine manifold vacuum. Vacuum switches thermactor air from downstream (past EGO sensor) to upstream (before EGO sensor) when solenoid is energized. Used on Ford MCU feedback carburetor system.

THERMACTOR AIR SYSTEM – Efficiency of catalytic converter is dependent upon temperature and chemical makeup of exhaust gases. These requirements are met by the thermactor air supply system.

THERMISTOR – A variable resistor which changes its resistance in relation to ambient temperature.

THM – Turbo Hydra-Matic

THREE-WAY CATALYST – Combines 2 converters in 1 shell. Controls NOx, HC and CO. Also called dual catalytic converter.

THROTTLE POSITION SENSOR (TPS) – A variable resistance (potentiometer) sensor which senses position proportional to the throttle position. The TPS is used to define the engine operating mode: either closed, part-throttle or wide open throttle (WOT).

TI – Transistorized Ignition System

TIC – Thermal Ignition Control (Chrysler)

TIMING – Generally refers to relationship between spark plug firing and piston position, (it can also refer to cam and valve timing) timing is most commonly expressed in crankshaft degrees before or after Top Dead Center (TDC) of the compression stroke.

TIV – Thermactor Idle Vacuum Valve (Ford)

TK – Throttle Kicker Actuator (Ford)

TK – Throttle Kicker solenoid, when energized, supplies manifold vacuum to throttle kicker actuator as directed by computer to compensate for engine loads. Also called idle-up system.

TKS – Throttle Kicker Solenoid

TOT – Transmission Oil Temperature

TP – Throttle Position sensor or its circuit. Used to signal computer the position of the throttle plates.

TP – Throttle Position

TP Mode – Throttle Position Mode

TPCV – Tank Pressure Control Valve

TPI – Tuned Port Injection

TPM – Tire Pressure Monitor

TPP – Throttle Position Potentiometer

TPS – Throttle Position Sensor

TPT – Throttle Position Transducer (Chrysler)

TR – Transmission Range Sensor

TRANSDUCER – A device which is actuated by power from one system and supplies power (usually in another form) to a second system. A typical transducer in automotive applications is an electrically actuated vacuum regulator.

Trip – A Trip for a particular Monitor requires that the vehicle is being driven in such a way that all the required "Enabling Criteria" for the Monitor to run and complete its diagnostic testing are met. The "Trip Drive Cycle" for a particular Monitor begins when the ignition key is turned "On." It is successfully completed when all the "Enabling Criteria" for the Monitor to run and complete its diagnostic testing are met by the time the ignition key is turned "Off." Since each of the eleven monitors is designed to run diagnostics and testing on a different part of the engine or emissions system, the "Trip Drive Cycle" needed for each individual Monitor to run and complete varies.

Trip Drive Cycle – Vehicle operation that provides the necessary driving condition to enable a vehicle Monitor to run and complete its diagnostic testing.

TRLHP – Thermal Vacuum Valve

TRS, TRS+1 – Transmission Regulated Spark Control System

TSB – Technical Service Bulletin

TSP – Throttle Solenoid Positioner (Ford)

TSS – Transmission Shaft Speed Sensor

TSS – Turbine Speed Shaft Sensor

TTS – Transmission Temperature Switch.

Tuned Port Injection – A type of MFI with intake tubes designed to be tuned for performance. Most TPI engines are also SFI.

TV – Throttle Valve

TVS – Temperature Vacuum Switch.

TVV – Thermal Vent Valve (Ford)

TWC – Three Way Catalyst

TWC – Three-Way Catalyst.

TWC + OC – Three Way Catalyst

UART – Universal Asynchronous Receiver-Transmitter

UD – Underdrive

UIDI – Up-Integrated Direct Ignition

UP-SHIFT LIGHT – An indicator, primarily controlled by engine speed and manifold vacuum, which provides a visual indication of when to shift to the next higher gear to obtain maximum fuel economy.

V – Volts

VAC – Vacuum

VACUUM – Describes a pressure that is less than atmospheric pressure; negative pressure.

VACUUM ADVANCE – A method of advancing ignition timing based on engine load conditions. Vacuum advance is accomplished by using engine intake manifold vacuum to operate the distributor diaphragm.

VACUUM CHECK VALVE (VCV) – A one-way flow control valve used to retain a vacuum signal in system after the vacuum source is gone.

VACUUM REGULATOR – A device which provides a constant vacuum output when vehicle is at idle, and switches to engine vacuum when the vehicle is at off idle.

VACUUM REGULATOR/SOLENOID – A regulator valve, under control of the vehicle's on-board computer, which provides vacuum to the feedback carburetor.

VACUUM RETARD DELAY VALVE (VRDV) – Delays a decrease in vacuum at the distributor vacuum advance until the source of vacuum decreases.

VAF – Vane Air-Flow sensor or its circuit.

VAF – Volume Air Flow

VAT – Vane Air Temperature Sensor

VAT – Vane Air-Flow Temperature sensor.

VATS – Vehicle AntiTheft System

VBAT – Vehicle (system) Battery Voltage

VCC – Vacuum Cut Control Solenoid

VCM – Vehicle Control Module

VCRM – Variable Control Relay Module

VCTS – Vacuum Control Temperature Sensing Valve (Ford)

VCV – Vacuum Control Valve (Ford)

VDOT – Variable Displacement Orifice Tube

VDV – Vacuum Delay Valve

VDV – Vacuum Differential Valve (Ford)

VECI – Vehicle Emission Control Information Decal

VEHICLE EMISSION CONTROL INFORMATION (VECI) – Factory specifications for servicing the vehicle's emission system. The VECI decal is located in engine compartment.

VF – Vacuum Fluorescent

VIM – Vehicle Interface Module

VIN – Vehicle Identification Number

VIS – Variable Induction System

VLCM – Variable Load Control Module

VM – Vane Meter or air flow meter.

VMV – Vacuum Modulator Valve

VMV – Vapor Management Valve (EVAP)

VNT – Variable Nozzle Turbocharger

VOLTAGE – The electromotive force that moves electrons through a conductor. One volt moves one ampere of current through one ohm of resistance.

VOLUMETRIC EFFICIENCY – Volumetric efficiency is a combination between ideal and actual efficiency of an internal combustion engine. In actual operation, volumetric efficiency is lowered by the inertia of gases, friction between gases and manifolds, the temperature of gases, and the pressure of air entering the engine. If the engine was able to completely fill each cylinder on the intake stroke, volumetric efficiency would be 100%.

VOTM – Vacuum Operated Throttle Modulator (Ford)

VPWM – Variable Pulse Width Modulated

VPWR – Ignition Switched Power

VR – Voltage Regulator

VR/S – Vacuum Regulator/Solenoid (Ford)

VRDV – Vacuum Retard Delay Valve (Ford)

VREF – Reference Voltage (from PCM)

VRESER – Vacuum Reservoir (Ford)

VREST – Vacuum Restrictor (Ford)

VRIS – Variable Resonance Induction System

VRS – Variable Reluctance Sensor

VRV – Vacuum Regulator Valve (Ford)

VSS – Vehicle Speed Sensor

VVA – Venturi Vacuum Amplifier (Ford)

VVC – Variable Voltage Choke (Ford)

VVV – Vacuum Vent Valve (Ford)

W/B – Wheelbase

WAC – WOT A/C Cutout Relay

WACA – A/C WOT Cutout Relay Monitor

Warm-up Cycle – Vehicle operation after an engine off period where engine temperature rises at least 40℉ (22℃) from its temperature before starting, and reaches at least 160℉ (70℃). The PCM uses warm-up cycles as a counter to automatically erase a specific code and related data from its memory. When no faults related to the original problem are detected within a specified number of warm-up cycles, the code is erased automatically.

WASTEGATE CONTROL SOLENOID – Controls the boost output on turbocharged engines. The vehicle's computer adjusts the duty cycle of the solenoid to provide maximum boost under varying operating conditions.

WOT – Wide Open Throttle or Wide Open Throttle switch.

WOT – Wide Open Throttle

WOTV – Wide-Open Throttle Valve (Ford)

WSS – Wheel Speed Sensor

WU OC – Warm Up Oxidation Catalytic Converter

WU TWC – Warm Up Three Way Catalytic Converter

ZONED VACUUM SWITCHES – 3 switches used on Ford MCU system that provides input signals to MCU, regarding engine load.