Knock Sensor: Description and Operation

PURPOSE
The Knock Sensor Signal informs the Engine Control Module (ECM) of predetonation or "ping".


OPERATION
Predetonation of a cylinder "charge" causes a shock wave to be sent through the engine block assembly. The piezoelectric crystal that is the Knock Sensor reacts to mechanical force associated with shock wave by discharging a small electric current. This signal is then sent to the ECM which will then retard the ignition timing.