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Appendix B – Glossary
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
AFC:
Air Flow Control
ALDL:
Assembly Line Diagnostic Link. Former name for GM (only) Data Link Connector,
the connector socket into which the scan tool plug is inserted; sometimes used to
refer to any pre-OBD II computer signals
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