The Knock Sensor (KS) system retards the spark timing up to 20 degrees in order to reduce the spark knock (detonation) in the engine. The engine uses the maximum spark advance in order to improve the driveability and the fuel economy.

Varying octane levels in today's gasoline can cause detonation in an engine. Detonation is called spark knock.

The KS system has three components:

The knock sensor detects abnormal vibration (spark knocking) in the engine. The sensor is mounted in the engine block near the cylinders. The KS module receives the knock sensor information and sends a signal to the ECM. The ECM then adjusts the spark timing in order to reduce the spark knocking.

The KS module sends a voltage signal (8 to 10 volts) to the ECM when the knock sensor does not detect any spark knocking, and the ECM provides normal spark advance.

When the knock sensor detects a spark knock, the module turns OFF the circuit to the ECM. The ECM then retards spark timing in order to reduce the spark knock.