Knock Sensor: Description and Operation

Purpose:
Varying octane levels in todays gasoline can cause detonation in high performance engines. Detonation is sometimes called spark knock.

To control spark knock, an Electronic Spark Control (ESC) system is used. This system is designed to retard spark timing up to 20° to reduce spark knock in the engine. This allows the engine to use maximum spark advance to improve driveability and fuel economy.

Operation:
The ESC knock sensor detects abnormal vibration (spark knocking) in the engine. The sensors produce an AC output voltage which increases as the amount of knock increases. This signal voltage is input to the ECM. The ECM adjusts the Electronic Spark Timing (EST) to reduce spark knock.

Location:
The knock sensor is located in the lower right side of the engine block.