Knock Sensor: Description and Operation

PURPOSE
When the knock sensor detects a knock in one of the cylinders, it sends an input signal to the PCM. In response, the PCM retards ignition timing for all cylinders by a scheduled amount.

OPERATION
The knock sensor threads into the side of the cylinder block in front of the starter motor.

Knock sensors contain a piezoelectric material which constantly vibrates and sends an input voltage (signal) to the PCM while the engine operates.
- As the intensity of the crystal's vibrations increase, the knock sensor output voltage also increases.

CAUTION: Over or under tightening effects knock sensor performance -- possibly causing improper spark control.