Knock Sensor: Description and Operation

PURPOSE
The knock sensor detects engine knock and sends a signal to the ECU. When knocking occurs, the ECU retards ignition timing until knock ceases.

LOCATION
Top of engine block between cylinder heads.

OPERATION
The knock sensor contains a crystal element with electrodes attached to opposing sides. When the crystal structure is distorted, a small voltage potential is created between opposite sides. When a knock of sufficient intensity and frequency occurs, the crystal is distorted slightly, generating a voltage signal that the ECU can detect.