Knock Sensor: Description and Operation

PURPOSE
Two knock sensors, located one on the side of each cylinder head, detect engine knock and send a signal to the ECU. When knocking occurs, the ECU retards ignition timing until knock ceases.

OPERATION
The knock sensors 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.