Knock Sensor: Description and Operation

KNOCK SENSORS

A pair of knock sensors monitors engine noise and vibration for the ECM. Engine knock is often caused by detonation or pre-ignition which can damage pistons and valves. The ECM is able to identify the characteristics of engine knock and retard ignition timing when knock is present. The ability to sense engine knock allows the ECM to operate the engine close to its limits of ignition advance. This is the most efficient ignition timing for maximum performance and fuel economy.

The sensors are mounted in the cylinder block located between cylinders 3 and 5 and between cylinders 4 and 6. Positioning a sensor in each bank of cylinders allows the ECM to precisely identify which of the eight cylinders is knocking.