Knock Sensor: Description and Operation

Knock Sensor:

Knock Sensor Cut-away:

Purpose

The Knock Sensor (KS) system is used to detect engine detonation. The PCM 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 AC voltage produced is proportional to the amount of knock.

Operation

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 PCM will learn the minimum and maximum frequency of the noise the engine produces. When the PCM determines that this frequency is less than or greater than the expected amount, a knock sensor DTC will set.