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KM: OBD II Glossary learn more
What is meaning in OBD II test and result interprete
PID Definitions PID Definitions
A/C: Air Conditioner
A/D: Analog to Digital
A/F: Air/Fuel ratio. The proportion of air and fuel delivered to the cylinder for
combustion. For example, an A/F ratio of 14:1 denotes 14 times as much air as
fuel in the mixture. Ideally the A/F ratio is 14.7:1.
ABS: Anti-lock Brake System
A/C Clutch Relay: The PCM uses this relay to energize the A/C clutch, turning the A/C compressor
on or off.
A/C Pressure Sensor: Measures air conditioning refrigerant pressure and sends a voltage signal to the
PCM.
A/C Pressure Switch: A mechanical switch connected to the A/C refrigerant line. The switch is
activated (sending a signal to the PCM) when the A/C refrigerant pressure
becomes too low or high.
Actuator: Actuators such as relays, solenoids, and motors allow the PCM to control the
operation of vehicle systems.
Air Injection Reaction (AIR) System:
An emission control system operated by the PCM. During cold starts, an air
pump injects outside air into the exhaust manifold to help burn hot exhaust
gases. This reduces pollution and speeds warm-up of oxygen sensors and
catalytic converters. After the engine is warm, the air will either be dumped back
to the atmosphere (or into the air cleaner assembly) or sent to the catalytic
converter.
APP: Acceleration Pedal Position (Sensor)
ASR: Acceleration Slip Regulation
Bank x: The standard way of referring to the bank of cylinders containing cylinder #x.
In-line engines have only one bank of cylinders. Most commonly used to identify
the location of oxygen sensors. See O2S, Sensor x, Sensor x.
BARO: Barometric Pressure Sensor. See MAP Sensor.
BBV: Brake Boost Vacuum (Sensor)
Glossary Glossary
B
BCM: Body Control Module
Boost Control Solenoid: A solenoid that is energized by the PCM, in order to control turbo/supercharger
boost pressure.
Brake Switch Signal: An input signal to the PCM indicating that the brake pedal is being pressed. This
signal is typically used to disengage Cruise Control systems and Torque
Converter Clutch (TCC) solenoids. See also TCC.
CAM: Camshaft Position Sensor. Sends a frequency signal to the PCM in order to
synchronize fuel injector and spark plug firing.
Catalytic Converter: Designed to reduce exhaust emissions.
CAN: Controller Area Network
CARB: California Air Resources Board. Governing body for emissions control in
California.
CKP REF: Crankshaft Position Reference.
CKP: Crankshaft Position. See CPS.
CKT: Circuit
Closed Loop (CL): A feedback system that uses the O2 Sensor(s) to monitor the results of
combustion. Based on the signal(s) from the O2 sensor(s), the PCM modifies
the air/fuel mixture to maintain optimum performance with lowest emissions. In
closed loop mode, the PCM can fine tune control of a system to achieve an exact
result.
CMP: Camshaft Position Sensor
CO: Carbon Monoxide; odorless gas produced by incomplete combustion.
Code Scanner: A device that interfaces with and communicates information via a data link.
Continuous Memory Codes: See Pending Codes.
CPS: Crankshaft Position Sensor. Sends a frequency signal to the PCM. It is used to
reference fuel injector operation and synchronize spark plug firing on
distributorless ignition systems (DIS).
CTS: Coolant Temperature Sensor. A resistance sensor that sends a voltage signal
to the PCM indicating the temperature of the coolant. This signal tells the PCM
whether the engine is cold or warm.
CVRTD: Continuous Variable Real Time Damping
D/R: Drive/Reverse
Data Link Connector (DLC): Connector providing access and/or control of the vehicle information, operating
conditions, and diagnostic information. Vehicles with OBD II use a 16-pin
connector located in the passenger compartment.
Data Stream: The actual data communications sent from the vehicles PCM to the data
connector.
DEPS: Digital Engine Position Sensor.
Detonation: See Knock.
DI/DIS: Direct Ignition/Distributorless Ignition System. A system that produces the
ignition spark without the use of a distributor.
DPFE: Differential Pressure Feedback Exhaust Gas Recirculation Sensor
DTC: Diagnostic Trouble Code. An alphanumeric identifier for a fault condition
identified by the On Board Diagnostic System.
Duty Cycle: A term applied to signals that switch between on and off. Duty cycle is the
percentage of time the signal is on. For example, if the signal is on only one
fourth of the time, then the duty cycle is 25%. The PCM uses duty cycle type
signals to maintain precise control of an actuator.
EBCM: Electronic Brake Control Module
EBTCM: Electronic Brake/Traction Control Module
ECM :Engine Control Module or Electronic Control Module
ECT: Engine Coolant Temperature sensor. See CTS.
EEPROM: Electrically Erasable Programmable Read Only Memory
EFE: Early Fuel Evaporation
EFI: Electronic Fuel Injection. Any system where a computer controls fuel delivery to
the engine by using fuel injectors.
EGR: Exhaust Gas Recirculation. The PCM uses the EGR system to recirculate
exhaust gases back into the intake manifold to reduce emissions. EGR is used
only during warm engine cruise conditions.
EOP: Engine Oil Pressure (Switch)
EOT : Engine Oil Temperature (Sensor)
EPA: Environmental Protection Agency.
ESC: Electronic Spark Control. An ignition system function that warns the PCM when
knock is detected. The PCM then retards spark timing to eliminate the knocking
condition.
EST: Electronic Spark Timing. An ignition system that allows the PCM to control spark
advance timing. The PCM determines optimum spark timing from sensor
information engine speed, throttle position, coolant temperature, engine load,
vehicle speed, Park/Neutral switch position, and knock sensor condition.
EVAP: Evaporative Emissions System.
FC: Fan Control
Freeze Frame: A block of memory containing DTCs of the vehicle operating conditions for a
specific time.
FTP: Federal Test Procedure. Strict test of vehicles emissions.
Ground (GND): An electrical conductor used as a common return for an electric circuit(s) and
with a relative zero potential (voltage).
Hall Effect Sensor: Any of a type of sensor utilizing a permanent magnet and a transistorized Hall
Effect switch. Hall Effect type sensors may be used to measure speed and
position of the crankshaft or camshaft for spark timing and fuel injector
control.
HO2S: Heated Oxygen Sensor. See O2S.
HVAC: Heating, Ventilation & Air Conditioning (System)
I/M: Inspection and Maintenance. An emission control program.
IAC: Idle Air Control. A device mounted on the throttle body which adjusts the amount
of air bypassing a closed throttle so that the PCM can control idle speed.
IAT: Intake Air Temperature (Sensor)
ICM: Ignition Control Module.
IMRC: Intake Manifold Runner Control
IPC: Instrument Panel Cluster
ISC: Idle Speed Control. A small electric motor mounted on the throttle body and
controlled by the PCM. The PCM can control idle speed by commanding the ISC
to adjust its position.
ISO: International Organization of Standardization also know as International
Standards Organization.
KAM: Keep Alive Memory
Knock Sensor (KS): Used to detect engine detonation or knock. The sensor contains a piezoelectric
element and is threaded into the engine block. Special construction makes the
element sensitive only to engine vibrations associated with detonation.
Knock: Uncontrolled ignition of the air/fuel mixture in the cylinder. Also referred to as
detonation or ping. Knock indicates extreme cylinder pressures or hotspots
which are causing the air/fuel mixture to detonate prematurely.
KOEO: Key On Engine Off. Turn the ignition key to on, but dont start engine.
KOER: Key On Engine Running. Start the vehicle.
LCD: Liquid Crystal Display
LTFT: Long Term Fuel Trim
M/T: Manual transmission or manual transaxle.
MAF: Mass Air Flow (sensor). Measures the amount and density of air entering the
engine and sends a frequency or voltage signal to the PCM. The PCM uses this
signal in its fuel delivery calculations.
MAP: Manifold Absolute Pressure (sensor). Measures intake manifold vacuum or
pressure and sends a frequency or voltage signal (depending on sensor type)
to the PCM. This gives the PCM information on engine load for control of fuel
delivery, spark advance, and EGR flow.
MAT: Manifold Air Temperature (sensor). A resistance sensor in the intake manifold
that sends a voltage signal to the PCM indicating the temperature of the
incoming air. The PCM uses this signal for fuel delivery calculations.
MIL: Malfunction Indicator Lamp. The MIL is most commonly known as the Check
Engine or Service Engine Soon light. A required on-board indicator to alert the
driver of an emission-related malfunction.
Misfire: Caused by the air fuel ratio being incorrect.
Monitor: A test performed by the on-board computer to verify proper operation of
emission-related systems or components.
MPFI or MFI: Multi-Port Fuel Injection. MPFI is a fuel injection system using one (or more)
injector(s) for each cylinder. The injectors are mounted in the intake manifold,
and fired in groups rather than individually.
NOx: Oxides of Nitrogen. The system EGR and Camshafts injects exhaust gases into
the intake manifold to reduce these gases at the tailpipe.
O2S: Oxygen Sensor. Generates a voltage of 0.6 to 1.1 volts when the exhaust gas
is rich (low oxygen content). The voltage changes to 0.4 volts or less when the
exhaust gas is lean (high oxygen content). This sensor only operates after it
reaches a temperature of approximately 349.C (660.F). O2 sensors are usually
found both upstream and downstream of the catalytic converter. The PCM uses
these sensors to fine tune the air-fuel ratio and to monitor the efficiency of the
catalytic converter. See Bank 1, Bank 2, Sensor 1, Sensor 2.
OBD II: On-Board Diagnostics, Second Generation. OBD II is a U.S.
Government-mandated standard requiring all cars and light trucks to have a
common data connector, connector location, communication protocol, DTCs
and code definitions. OBD II first appeared on vehicles in late 1994, and is
required to be present on all cars sold in the US after January 1, 1996.
ODM: Output Device Monitor.
Open Loop (OL): A control system mode that does not monitor the output to verify if the desired
results were achieved. A fuel delivery system usually operates in open loop
mode during cold engine warm-up because the oxygen sensors are not yet
ready to send a signal. Without the oxygen sensor signal, the computer cannot
check the actual results of combustion.
PCM: Powertrain Control Module. The brains of the engine and transmission control
systems housed in a metal box with a number of sensors and actuators
connected via a wiring harness. Its job is to control fuel delivery, idle speed,
spark advance timing, and emission systems. The PCM receives information
from sensors, then energizes various actuators to control the engine. The PCM
is also known as the ECM (Engine Control Module).
Pending Codes: Also referred to as Continuous Memory codes and Maturing Diagnostic Trouble
Codes. Pending Codes may be set by emission related powertrain components
and systems. If the fault does not occur after a certain number of drive cycles,
the code is erased from memory.
PID: Parameter Identification. Identifies an address in memory which contains
vehicle operating information.
PNP: Park/Neutral Position. A switch that tells the PCM when the gear shift lever is
in the Park or Neutral position. When in Park or Neutral, the PCM operates the
engine in an idle mode.
PROM: Programmable Read-Only Memory. The PROM contains programming
information the PCM needs to operate a specific vehicle model/engine
combination.
PSPS: Power Steering Pressure Switch
Purge Solenoid: Controls the flow of fuel vapors from the carbon canister to the intake manifold.
The canister collects vapors evaporating from the fuel tank, preventing them
from escaping to the atmosphere and causing pollution. During warm engine
cruise conditions, the PCM energizes the Purge Solenoid so the trapped vapors
are drawn into the engine and burned.
PWM: Pulse Width Modulated
PZM: Platform Zone Module
QDM: Quad Driver Module
RAM: Random Access Memory
Relay: An electromechanical device in which connections in one circuit are switched.
Reluctance Sensor:
A type of sensor typically used to measure crankshaft or camshaft speed and/or
position, driveshaft speed, and wheel speed.
ROM: Read-Only Memory. Permanent programming information stored inside the
PCM, containing the information the PCM needs to operate a specific vehicle
model/engine combination.
RPM: Revolutions Per Minute
SAE: Society of Automotive Engineers.
Scan Tool: A device that interfaces with and communicates information on a data link.
SDM: Sensing and Diagnostic Module
Sensor x: A standard term used to identify the location of oxygen sensors. Sensor 1 is
located upstream of the catalytic converter. See O2S, Bank 1, Bank 2.
Sensor: Any device that reports information to the PCM. The job of the sensor is to
convert a parameter such as engine temperature into an electrical signal that the
PCM can understand.
SFI or SEFI: Sequential Fuel Injection or Sequential Electronic Fuel Injection. A fuel injection
system that uses one or more injectors for each cylinder. The injectors are
mounted in the intake manifold and are fired individually.
Solenoid: A device consisting of an electrical coil which when energized, produces a
magnetic field in a plunger, which is pulled to a central position. A solenoid may
be used as an actuator in a valve or switch.
STFT: Short Term Fuel Trim.
STS: Service Throttle Soon
TAC: Throttle Actuator Control
TBI: Throttle Body Injection. A fuel injection system having one or more injectors
mounted in a centrally located throttle body, as opposed to positioning the
injectors close to an intake valve port. TBI is also called Central Fuel Injection
(CFI) in some vehicles.
TCC: Torque Converter Clutch
TCM: Transmission Control Module
TCS: Traction Control System for PCM and brakes
TDC: Top Dead Center. When a piston is at its uppermost position in the cylinder.
TFP: Transmission Fluid Pressure
TFT: Transmission Fluid Temperature (Sensor)
Throttle Body: A device which performs the same function as a carburetor in a fuel injection
system. On a throttle body injection (TBI) system, the throttle body is both the
air door and the location of the fuel injectors. On port fuel injection systems (PFI,
MPFI, SFI, etc.), the throttle body is simply an air door. Fuel is not added until
the injectors at each intake port are activated. In each case, the throttle body is
attached to the accelerator pedal.
TPS: Throttle Position Sensor. Potentiometer-type sensor connected to the throttle
shaft. Its voltage signal output increases as the throttle is opened. The PCM
uses this signal to control many systems such as idle speed, spark advance, fuel
delivery, etc.
Traction Assist: Assist in traction with brakes only.
Trip: Vehicle operation for a period of time so the systems can be monitored.
TTS: Transmission Temperature Sensor. A resistance sensor mounted in the
transmission housing in contact with the transmission fluid. It sends a voltage
signal to the PCM indicating the temperature of the transmission.
VECI: Vehicle Emission Control Information. A decal located in the engine
compartment containing information about the emission control systems found
on the vehicle. The VECI is the authoritative source for determining whether a
vehicle is OBD II compliant.
VIN: Vehicle Identification Number. This is the factory-assigned vehicle serial
number. This number is stamped on a number of locations throughout the
vehicle, but the most prominent location is on top of the dashboard on the
drivers side, visible from outside the car. The VIN includes information about the
car, including where it was built, body and engine codes, options, and a
sequential build number.
VSS: Vehicle Speed Sensor. Sends a frequency signal to the PCM. The frequency
increases as the vehicle moves faster to give the PCM vehicle speed
information used to determine shift points, engine load, and cruise control
functions.
VTD: Vehicle Theft Deterrent
Warm-up Cycle: Warm-up cycle is when the engine coolant temperature rises at least 40 degrees
above that at engine start up.
WOT: Wide-Open Throttle. The vehicle operating condition brought about when the
throttle is completely (or nearly) open. The PCM typically delivers extra fuel to
the engine and de-energizes the A/C compressor at this time for acceleration
purposes. The PCM uses a switch or the TPS to identify the WOT condition.
