C 3500 Truck 2WD V8-454 7.4L VIN J SFI (1999)
Knock Sensor: Description and Operation
Knock Sensor (KS) Sensor
Knock Sensor (KS)
The Knock Sensor (KS) system is used in order to detect the engine detonation. The VCM will retard the spark timing based on the signals from the KS
module. The knock Sensor(s) produce an AC voltage that is sent to the KS module. The amount of the AC voltage produced is proportional to the
amount of knock.
An operating engine produces a normal amount of engine mechanical vibration (Noise). The knock sensor(s) will produce an AC voltage signal from this
Noise. When an engine is operating, the VCM will learn the minimum and maximum frequency of the noise that the engine produces. When the VCM
determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set.
