G 2500 3/4 Ton Van V8-350 5.7L VIN K TBI (1995)
Knock Sensor: Description and Operation
DESCRIPTION
Varying octane levels in today's gasoline can cause detonation (also known as spark knock) in an engine.
The Knock Sensor (KS) system has a knock sensor that are used on all engines. The KS system reduces spark knock (detonation) in the engine.
This allows the engine to have maximum spark advance for improved driveability and fuel economy.
OPERATION
A control module PCM is used in conjunction with knock sensors to control detonation. On PCM applications no KS module will be found as it is
internal to the control module.
A 5 volt reference is applied to the knock sensors which have an internal resistance of about 3900 ohms each. This resistance combined will lower
the applied voltage to about half or 2.5 volts. When a knock is present, a small AC voltage is produced by the knock sensors and transmitted to the
PCM riding on top of the already existing 2.5 volts. An AC voltage monitor inside the PCM will detect the knock and trigger the PCM to start
retarding the spark incrementally.
