Knock Sensor: Description and Operation

KNOCK SENSORS - PCM INPUT

Knock Sensor Locations 1997:

The engine has two knock sensors. The knock sensors bolt into the top of the cylinder block below the cylinder heads. The sensors monitors both the right and left bank of cylinders. When the knock sensors detect a knock in one of the cylinders, they send an input signal to the PCM. In response, the PCM retards ignition timing by a scheduled amount.

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

NOTE: Over or under tightening effects knock sensor performance, possibly causing improper spark control.