Knock Sensor: Description and Operation

Spark knock (detonation) is controlled by an electronic spark control (ESC) system that can retard ignition timing up to 20°. This allows the engine to use maximum spark advance to improve driveability and fuel economy.

The system consists of an ESC module and knock sensor. When the sensor detects knock, it produces a voltage signal that is sent to the ESC module. As long as the module receives no signal from the sensor, it sends a signal voltage (8 - 10V) to the ECM and the ECM calculates normal spark advance.

When the module receives a knock signal, it changes signal voltage to the ECM to zero volts and the ECM retards timing to reduce knock.