Knock Sensor: Description and Operation

Knock Sensor Operation:

LOCATION

Knock sensors thread into the cylinder block just below the cylinder heads.

PURPOSE

When a knock sensor detects a knock in one of the cylinders it sends a signal to the Powertrain Control Module (PCM). In response the PCM retards the ignition timing by a predetermined amount.

THEORY/OPERATION

Knock sensors contain a crystal which constantly vibrates and sends a voltage signal to the PCM while the engine operates. When spark knock occurs, the intensity of the crystals vibration increases, the knock sensor output voltage also increases signaling the PCM to retard ignition timing.