Knock Sensor: Description and Operation

KNOCK SENSOR-PCM INPUT

Knock Sensor:

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

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.

Knock sensors contain a piezoelectric material which sends an input voltage (signal) to the PCM. As, the intensity of the engine knock vibration increases, the knock sensor output voltage also increases.

KNOCK SENSOR
The knock sensor threads into the cylinder block.

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.

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 vibration increases, the knock sensor output voltage also increases.

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