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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 – COMBUSTION CONTROL COMPUTER
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.
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