Knock Sensor: Description and Operation

The Knock Sensor is an electro-mechanical device capable of measuring vibration and converting it into an electrical signal. During engine knock, a variation in pressure on the sensor body produces current, which is transmitted to the ECU through a cable consisting of two shielded wires. Proper spark advance is fully automatic, and is provided by a load table built into the ECU. When the knock sensor signals the ECU that pre-ignition is about to occur, the ECU will automatically retard ignition timing as required. When the threat of pre-ignition is eliminated as determined by engine load, the ECU will then slowly return ignition timing to its preset value.