Knock Sensor: Description and Operation

Knock Sensor:

PURPOSE
Efficient combustion occurs just prior to pre-ignition. The knock sensor detects internal engine vibrations, caused by pre-ignition, and reports to the Engine Control Module (ECM).

OPERATION
When pre-ignition occurs, the sensor produces a low voltage to the ECM signalling the knock has been detected. The ECM then modifies fuel delivery and spark timing as necessary to prevent the knock from recurring. the engine is allowed to run at peak efficiency while preventing internal damage.

CONSTRUCTION
The sensor consists of a specially tuned piezo-electric crystal and a weight.