Acronyms and Definitions

NOTE: This acronyms and definitions listing contains technical terms applicable to Ford Motor Company products. It is not intended to be an all-inclusive dictionary of components and their functions. If a detailed description of a particular system or component is desired, refer to the applicable article for the specific vehicle being repaired.

4V: Four valves per engine cylinder
ABS: Anti-Lock Brake System
A/C: Air Conditioning
A/CC: Air Conditioning Clutch
A/CCR: A/C Clutch Control Relay
A/CLPCS: A/C Low Pressure Cycling Switch
ACCS: Air Conditioning Cycling Switch
ACD: Air Conditioning Demand. A signal input to the PCM from the air conditioning control panel.
ACDS: Air Conditioning Diagnostic Switch (refrigerant containment switch)
ACET: Air Conditioning Evaporator Temperature (also be referred to as Evaporator Air Discharge Temperature)
ACP: Air Conditioning Head Pressure or A/C cycling switch input state
ACPSW: Air Conditioning Pressure Switch
ACPT: Air Conditioning Pressure Transducer (switch)
A/D: Analog-to-Digital. Analog-to-Digital signal conversion.
ADC: See ATDC.
Air/Fuel Ratio: Air-to-fuel mixture ratio. An air-to-fuel mixture that is 14.7:1 is also called stoichiometry.
Ambient Air Temperature: Temperature of the air surrounding an object
Analog (Electrical/Electronic): An electrical signal that can obtain any value within the voltage limits of the signal.
APP: Accelerator Pedal Position
ARB: Air Resource Board
ASCII: American Standard Code Information Interchange
ATDC: After Top Dead Center. The location of the piston after it has reached the top of its stroke. Measured in degrees of crankshaft rotation.
BARO: Barometric Pressure
Base Timing: Spark advance in degrees before top dead center of the base engine without any control from the PCM.
Battery Positive Voltage (B+): The positive (+) voltage from the battery or any circuit connected directly to the battery.
BATTEMP: Battery Temperature
BJB: Battery Junction Box
BPA: Brake Pedal Applied. Typically located on the braking system master cylinder. Can be hydraulic or electric.
BPO: Battery Power Off
BPP: Brake Pedal Position
BPS: Brake Pedal Switch/Speed Control Deactivation
BSI: Brake Shift Interlock
BTDC: Before Top Dead Center. The location of the piston before it has reached the top of its stroke. Measured in degrees of crankshaft rotation.
Bus + or Bus -: Multiplex circuits that carry controller area network (CAN) data from module to module and to the data link connector (DLC).
BVREF: Buffer Voltage Reference. A dedicated circuit that provides an approximately 5-volt signal used as a reference by certain sensors.
CAFE: Corporate Average Fuel Economy. A set of federal requirements and regulations that govern fuel economy standards.
CANVNT: Canister Vent
CAN: Controller Area Network
Catalyst: Catalytic converter. An in-line exhaust system device used to reduce the level of engine exhaust emissions.
CCM: Comprehensive Component Monitor
CD A through D: Coil Driver 1 through 4
Centralized Testing Facility: State government operation. Provides inspection/maintenance (IM) and safety inspections.
CGND: Case Ground. Provides a ground source for the PCM or ECU case.
CHT: Cylinder Head Temperature. Units are displayed in degrees Fahrenheit or degrees Celsius.
CHTV: Cylinder Head Temperature Voltage
CKP: Crankshaft Position
CL: Closed Loop. An operating condition or mode that enables operation based on sensor feedback.
CMP: Camshaft Position. PCM input signal from the camshaft position sensor.
CMS: Catalyst Monitor Sensor. The downstream heated oxygen sensor (HO2S).
CMVSS: Canadian Motor Vehicle Safety Standards.
CO: Carbon Monoxide. A colorless, odorless and toxic gas that is a component of auto exhaust emissions.
CO₂ : Carbon Dioxide. A colorless, odorless gas that is a normal by-product of the combustion of fuel.
Coil: A device consisting of windings around an iron core. In a spark ignition system, designed to increase voltage.
Cold Soak: Time given to a vehicle to sit at a low temperature, typically below 20°C (68°F), until the temperature of external and internal components stabilizes.
CONT: Continuous Memory. The portion of keep alive memory (KAM) used to store DTCs generated during the continuous memory self-test.
Continuous Memory Self-Test: A continuous test of the electronic engine control (EEC) system conducted by the PCM whenever the vehicle is operating.
COP: Coil On Plug. Ignition coil on plug assembly.
CSE GND: Case Ground
CT: Closed Throttle. A mode when the PCM varies the pulse width of the fuel injectors to obtain the air/fuel mixture appropriate for closed throttle operation.
CTO: Clean Tach Output
DC: 1. Direct Current. Electric current flowing in 1 direction. 2. Duty Cycle. The voltage measurement of ON time versus the full cycle period, expressed in percent.
DCF: DC/DC Converter Fault
DCL: Data Communication Link. A communication path between various in-vehicle electronic modules. Accessed by scan tools through the data link connector (DLC).
Digital: Controls process information by switching the current or voltage ON and OFF.
DIS: Distributorless Ignition System. A system in which the ignition coil secondary circuit is sequenced without a distributor.
DLC: Data Link Connector. J1962 connector providing access to vehicle diagnostic information.
DMM: Digital Multimeter
DOHC: Dual Overhead Cam. An engine configuration that uses 2 camshafts positioned above the valves.
DTM: Diagnostic Test Mode. A level of capability in an on board diagnostics (OBD) system.
DTC: Diagnostic Trouble Code. An alpha/numeric identifier for a concern identified by the OBD system.
ECT: Engine Coolant Temperature. Displayed in degrees Fahrenheit or degrees Celsius.
ECVT: Electronically Controlled Continuously Variable Transaxle
EEC: Electronic Engine Control
EEC-V: Fifth-generation EEC system
EEGR: Electric Exhaust Gas Recirculation
EEPROM: Electrically Erasable Programmable Read-Only Memory. An electronic component in the PCM that allows the electronic storage of information.
EGR: Exhaust Gas Recirculation. A process in which a small amount of exhaust gas is routed into the combustion chamber.
EGRMC (1-4): Electric Exhaust Gas Recirculation Motor Control
EGRT: Exhaust Gas Recirculation Valve Temperature. A temperature sensor that is threaded into the bottom of the intake plenum.
EI: Integrated Electronic Ignition. An electronic ignition system that has the ignition control module (ICM) integrated into the PCM.
EI-LDR: Electronic Ignition-Low Data Rate
EMI: Electromagnetic Interference. Usually caused by ignition voltage spikes, solenoids, relay operation, or noisy generator contacts.
EOL: End of Line. A system designed specifically for use at assembly plants to make sure all new vehicles conform to design specifications.
EOT: Engine Oil Temperature
EPA: Environmental Protection Agency
ESM: EGR System Module
ETC: Electronic Throttle Control
ETCVREF: Voltage Reference (5V) for ETC (APP BVREF, TP BVREF)
EVAP: Evaporative Emissions. A system to prevent fuel vapor from escaping into the atmosphere.
Evaporative Emissions Canister: An evaporative emission canister containing activated charcoal that absorbs and holds fuel vapors.
EVO: Electronic Variable Orifice
EVMV: Electric Vapor Management Valve. Also known as the EVAP canister purge valve.
Exciter Ring: A toothed or notched iron or steel disk that is the moveable part of a speed sensor.
FAN: Fan Speed
FC: Fan Control
FCS: Fuel Control Solenoid
FCIL: Fuel Cap Indicator Lamp. Indicates the fuel filler cap is not correctly installed.
FEAD: Front End Accessory Drive
FEPS: Flash EEPROM Programming Signal. 18-volt DC signal sent by the scan tool to initiate PCM reprogramming.
FLI: Fuel Level Input. Used by the EVAP monitor to calculate fuel tank vapor volume. Displayed as a percentage.
FLI V: Fuel Level Input Voltage
FMEM: Failure Mode Effects Management. Operating strategy that maintains limited vehicle function in the event of a PCM or EEC component failure.
FP: 1. Fuel Pump. Indicates whether the pump has been commanded ON or OFF by the PCM. 2. Fuel Pump (Modulated). Fuel pump duty cycle percentage.
FPC: Fuel Pump Control
FPDM: Fuel Pump Driver Module. A module that controls the electric fuel pump.
FPM: Fuel Pump Monitor. Monitors the fuel pump/circuits for concerns.
Freeze Frame: A block of memory containing the vehicle operating conditions at a specific time.
FRP: Fuel Rail Pressure
FRPT: Fuel Rail Pressure Temperature Sensor
FRT: Fuel Rail Temperature
FSC: Fail-Safe Cooling
FTIV: Fuel Tank Isolation Valve
FTP: Fuel Tank Pressure
Fuel Tank Vapor Valve: A valve mounted in the top of the fuel tank that vents excess vapor and pressure from the fuel tank into the evaporative emission control system.
FWD: Front-Wheel Drive
GCU: Generator Control Unit
GND: Ground
GPM: Grams per Mile. Also known as Gallons per Minute.
Green State Vehicle: Formally known as California Emissions. A vehicle that is equipped with California on board diagnostics.
GSDN: Generator Motor Shutdown
GVW: Gross Vehicle Weight
Hall Effect: A process where current is passed through a small portion of semiconductor material and a magnetic field to produce a small voltage in the semiconductor.
Hard Fault: A concern currently present in the system.
HC: 1. Hydrocarbon. A by-product of combustion and a component of auto exhaust emissions. 2. High Compression.
HLOS: Hardware Limited Operating Strategy. A mode of operation where the PCM uses fixed values in response to internal PCM concerns in place of output commands.
HO2S: Heated Oxygen Sensor. Provides information on rich or lean exhaust conditions to the PCM.
Hot Soak: Period of time after an engine operates where localized combustion heat dissipates throughout the engine.
HVIL: High Voltage Interlock Circuit
HVIN: High Voltage Interlock Negative Circuit
HVIP: High Voltage Interlock Positive Circuit
HVN: High Voltage Negative Circuit
HVP: High Voltage Positive Circuit
Hydrogen: Chemical symbol H. Highly flammable gas.
Hz: Hertz. Cycles per second.
IAT: Intake Air Temperature
IC: Integrated Circuit. A small semi-conductor device capable of doing many separate circuit functions.
IFS: Inertia Fuel Shut Off
IGN GND: Ignition Ground
Ignition: System used to provide high voltage spark for engines.
IMAP: Inferred Manifold Absolute Pressure (MAP)
INJ1, INJ2, INJ3, INJ4: Injector number or its signal output from the PCM.
Injector: A device for delivering metered pressurized fuel to the intake system or the cylinders.
Intake Air: Air drawn through a filter and distributed to each cylinder for use in combustion.
IPC: Independent Plausibility Checker
ISDN1, ISDN2: Immediate Shutdown Circuits 1 and 2
ISP-R: Ignition Switch Position RUN Circuit
ISP-R/S: Ignition Switch Position START Circuit
ISO: International Standards Organization
ITCC: Intelligent Torque-Controlled Coupling
KAM: Keep Alive Memory. A portion of the memory within the PCM that must have power even when the vehicle is not operating.
KAPWR: Keep Alive Power. A dedicated and unswitched power circuit that maintains KAM.
KEYPWR: Key Power. Battery voltage supplied when the key is in the ON position.
Knock: A sharp metallic sound produced when 2 combustion pressure fronts collide in the combustion chamber of an engine.
KOEO Self-Test: Key On Engine Off Self-Test. A test of the EEC system conducted by the PCM with power applied and the engine at rest.
KOER Self-Test: Key On Engine Running Self-Test. A test of the EEC system conducted by the PCM with the engine running and the vehicle at rest.
Km/h: Kilometers per Hour
kPa: Kilopascal. Unit of pressure. 3.386 kPa equals 1 inch of mercury (Hg).
KS1: Knock Sensor Bank 1. Detects engine knock.
L: Liters. The unit of volume in the metric measuring system. One liter equals 1.06 quarts.
LDR: Low Data Rate. Type of misfire monitor.
LOAD: Calculated Engine Load
LONGFT1: Long-Term Fuel Trim Bank 1. Fuel flow adjustment determined by the PCM.
LOOP: Indicates OPEN or CLOSED loop status.
LOS: Limited Operating Strategy
MAF: Mass Air Flow
MAF RTN: Mass Air Flow Return. A return circuit for the MAF sensor.
MAP: Manifold Absolute Pressure. The internal pressure of the intake manifold.
MCLTEMP: Traction Motor Coil Temperature
MCU: Motor Control Unit
MECP: Motor Electronics Coolant Pump
MECT: Motor Electronics Coolant Temperature
Microprocessor: A device that controls logic and arithmetic functions.
MIL: Malfunction Indicator Lamp. An indicator lamp alerting the driver of an emission related concern.
MISF: Misfire. Any event in the cylinder that causes a sudden change in acceleration of the crankshaft.
MSDN: Motor Shutdown
MY: Model Year
NC: Normally Closed
NGS: New Generation Self-Test Automatic Readout (STAR) tester
NO: Normally Open
NO_X : Oxides of Nitrogen. Formed at high combustion temperatures.
O2S: Oxygen Sensor. Provides information on rich or lean exhaust conditions to the PCM.
OASIS: On-line Automotive Service Information System
OBD, OBD-II: On Board Diagnostics, On Board Diagnostics Second Generation. A system that monitors PCM input and output control signals.
On-Demand Self-Test: The KOEO and KOER tests of the PCM and KOEO test of the TCM initialized by a technician.
OC: Oxidation Catalytic converter. A catalytic converter system that reduces the levels of HC and CO emissions.
OCT ADJ: Octane Adjust. Compensating strategy that adjusts for changes in fuel octane.
OEM: Original Equipment Manufacturer
OHC: Overhead Cam. An engine configuration that uses a single camshaft positioned above the valves.
Open Circuit: A circuit that does not provide a complete path for flow of current.
OL: Open Loop. An operating condition based on instructions not modified by PCM feedback.
OSC: Output State Control
OTM: Output Test Mode
Ozone: A blue gaseous form of oxygen (O₃ ) formed naturally by electric discharge or exposure to ultraviolet radiation.
PCM: Powertrain Control Module
PCV: Positive Crankcase Ventilation. A system that allows the controlled flow of crankcase vapors into the combustion chamber.
PF: Purge Flow. Amount of fuel vapor burned in the engine.
Photochemical: The action of light on air pollutants that results in creating smog.
PID: Parameter Identification. Identifies an address in PCM memory that contains operating information.
PIP: Profile Ignition Pickup. Provides crankshaft position information for ignition synchronization.
Potentiometer: An adjustable resistance component commonly used as a sensor (example: TP sensor).
Powertrain: Engine and transmission/transaxle components.
Pressure - Absolute: A pressure referenced to a perfect vacuum.
Pressure - Atmospheric: The pressure of the surrounding air at any given temperature and altitude. Sometimes called barometric pressure.
Pressure - Barometric: Atmospheric pressure or the results obtained by a barometer.
Pressure - Differential: The pressure difference between 2 regions, such as between the intake manifold and the atmospheric pressure.
Pressure - Gauge: The amount by which the absolute pressure exceeds the atmospheric pressure.
PRNDL: Gear Selector Position
PPM: Parts per Million. A measure used in emission analysis.
PROM: Programmable Read-Only Memory. Similar to read-only memory (ROM), except without program instructions.
Protocol: A set of rules for the exchange of information on a network.
PSC Module: Power Steering Control Module
PSR: Power Sustain Relay
PW: Pulse Width. The length of time an actuator, such as a fuel injector, remains energized.
PWM: Pulse Width Modulation. Controls the intensity of an output by varying the signal duty cycle.
PWR GND: Power Ground. The main ground circuit in the EEC system.
PZEV: Partial Zero Emission Vehicle
Quick Test: A series of diagnostic tests consisting of KOEO, KOER, and continuous memory self-tests. The resulting DTCs are retrieved using the scan tool.
RAM: Random Access Memory. Memory into which information can be written as well as read.
RDI: Restraint Deployment Indicator
REDOX: Reduction Oxidation Catalytic converter. A catalytic converter system designed to operate at high temperatures.
Relay: An electromechanical device in which connections in 1 circuit are opened or closed by changes in another circuit.
Repetitive Spark: Multiple firings of individual spark plugs at engine speeds below 1,000 RPM to improve idle quality and emissions.
RF: Radio Frequency
RFI: Radio Frequency Interference
RFS: Returnless Fuel System
RM: Relay Module. A module containing 2 or more relays.
ROM: Read-Only Memory. Computer memory that can be accessed and used, but not altered.
RON: Research Octane Number
Routine: A group of related tasks, such as a series of diagnostic tests.
RPM: Revolutions per Minute
RTN: Return. A dedicated sensor ground circuit.
RWD: Rear-Wheel Drive
SAE: Society of Automotive Engineers
Sensor: A device that detects the value or change in a physical quantity, such as temperature, pressure, or flow rate, and converts the data into an electrical signal.
SFI: Sequential Multiport Fuel Injection. A multiport fuel delivery system where each injector is individually energized and timed relative to its cylinder intake event.
Shield: A conducting sleeve that surrounds wires to be electronically isolated from electromagnetic interference (EMI).
Short Circuit: An undesirable condition in a circuit where the circuit termination is at a point other than that intended.
SHRTFT1: Short-Term Fuel Trim Bank 1. Fuel flow adjustment in response to the HO2S input during closed-loop operation.
SIG RTN: Signal Return. A dedicated sensor ground circuit that is common to 2 or more sensors.
Smart Driver: A PCM or ECU output driver that can detect concerns (open or shorts) on its output circuit.
Solenoid: An electrical coil that produces a magnetic field that changes the position of a metal plunger.
Stoichiometry: An air/fuel mixture that is neither too rich nor too lean. Stoichiometric ratio is 14.7 parts of air for every 1 part of fuel.
Switch: A device for making, breaking, or changing the connections in an electrical circuit.
TACM: Throttle Actuator Control Motor used in the ETC system.
TB: Throttle Body. A device that controls airflow through the engine via a butterfly valve and has an air bypass channel around the throttle plate.
TBCM: Traction Battery Control Module
TCM: Transaxle Control Module
TDC: Top Dead Center
Tear Tag: The 2-piece adhesive label attached to the PCM to identify its calibration.
TFT: Transmission Fluid Temperature.
TGAC: Torque of Generator AC signal
Thermistor: A temperature-dependent resistor used in CHT and ECT sensors.
Timing: The relationship between spark plug firing and piston position expressed in crankshaft degrees before (BTDC) or after (ATDC) top dead center of the compression stroke.
TMAC: Torque of Motor AC signal
TP: Throttle Position sensor. A potentiometer that provides throttle angle and rate information for the PCM.
TR Sensor: Transmission Range Sensor
TR-A Sensor: Analog Transmission Range Sensor. Provides information to the PCM on the transmission range selector position.
Transducer: A device that receives energy from one medium and transfers it to another. For example, thermal energy is converted to an electrical signal through a temperature probe.
Underspeed Mode: A control mode that prevents the engine from stalling in the event it stumbles while running. Also used during engine crank.
Vacuum: Manifold pressure that is reduced below the ambient atmospheric pressure.
Variable Reluctance: A process of passing a varying magnetic field through wire windings and inducing a voltage.
VBPWR: Vehicle Buffered Power. A PCM-supplied power source that supplies regulated voltage.
VC: Vehicle Certification
VECI: Vehicle Emission Control Information label
VIN: Vehicle Identification Number. A unique identification number given to every vehicle produced. Includes information about the year, model, engine, and plant origin of the vehicle.
VMV: Vapor Management Valve. Controls the flow of fuel vapors out of the carbon canister.
VPWR: Vehicle Power. A switched circuit that provides power to the EEC system. Compare Battery Voltage (B+).
VREF: Reference Voltage. A dedicated circuit that provides an approximately 5-volt signal used as a reference by certain sensors.
VSC: Vehicle System Controller
VSS: Vehicle Speed Sensor. A magnetic pickup device that generates an AC signal that is proportional to the vehicle speed.
WAC: Wide Open Throttle A/C Cut-Off. Turns the A/C system off during wide open throttle or certain other operating conditions.
WOT: Wide Open Throttle. A condition of maximum airflow through the throttle body.