Knock Sensor Operation

Fig. 15 Knock Sensor:

The knock sensor threads into the side of the cylinder block in front of the starter Fig. 15. 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 increase, the knock sensor output voltage also increases.

CIRCUIT OPERATION
The knock sensor provides an input to the Powertrain Control Module (PCM) on circuit K42. Circuit K42 connects to cavity 24 of the PCM connector.

The knock sensor is case grounded to the engine block.