Knock Sensor: Description and Operation

PURPOSE
Informs the Engine Control Module (ECM) of engine knock, so that engine timing and mixture can be adjusted to correct the potentially damaging preignition.

OPERATION
Tuned to vibrate sympathetically with vibrations characteristic of an engine with improper combustion. When vibrating, it generates a voltage signal.

CONSTRUCTION
A Piezoelectric sensing element, in a threaded housing. Installed as a pair, one for each cylinder head.