Glossary
GM
4-8
QUAD-DRIVER (QDM) –
Computer chip, in the PCM,
capable of operating four separate outputs. Some have digital
and some have pulse width modulated outputs.
RAP
– Retained Accessory Power.
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.
RICH MIXTURE
– Air/fuel mixture that has more fuel than
can burn completely, 1 part fuel to 14 or less parts air.
SAW
– Spark Advance Word, and also Spark Angle Word.
SCC
– Spark Control Computer.
SES
– Service Engine Soon light.
SEFI, SFI
– Sequential Fuel Injection, type of MFI with
injectors pulsed individually based on engine firing order.
SIG RTN
– Signal Return circuit for all sensors except HEGO.
SIL
– Shift Indicator Light. Indicates to driver optimum time
to shift gears.
SIR
– Supplemental Inflatable Restraint (SIR) system; air
bag.
SIS
– Solenoid Idle Stop.
SOLENOID
– Wire coil with a movable core which changes
position by means of electromagnetism when current flows
through the coil.
SPARK RETARD SOLENOID
– Output device that receives
an output signal to bleed distributor’s vacuum advance when
spark knock occurs.
SSI
– Solid State Ignition system.
T.V.
– Throttle Valve.
TAB
– Thermactor Air Bypass solenoid.
TACH INPUT
– Engine rpm signal sent to computer from
ignition coil primary circuit.
TAD
– Thermactor Air Diverter solenoid.
TBI
– Throttle Body Injection (Fuel).
TCC
– Torque Converter Clutch.
TCP
– Temperature Compensating Pump.
Summary of Contents for GM 3123
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