Knock Sensor: Description and Operation

Knock Sensor 1 Or 2:

Each of the two knock sensors is located on the front and rear of the engine block. The knock sensor is a piezoelectric flat response (wide resonant band) device that produces an AC voltage of different amplitude and frequency based on engine mechanical vibration. The amplitude and frequency are dependent on the level of knock the sensor detects. If the ECM detects knock activity, it can retard timing on individual cylinders until the spark knock is eliminated. The ECM will always work back towards zero compensation or no spark retard.