Knock Sensor: Description and Operation

Knock Sensor Schematic:

PURPOSE
The knock sensor senses engine detonation and reports to the ECM. The sensor input is used to determine proper ignition and injection timing. The ECM uses two sensors to record vibrations for the full length of the engine.

LOCATION
The sensors are mounted to the left side of the engine block.

CONSTRUCTION
Each sensor consists of a piezoelectric element tuned to resonate at the same frequency as engine knock (detonation).

OPERATION
When the engine knocks (detonates), the piezo element resonates at the same frequency and produces a voltage that varies according to the amplitude of the knock. This voltage is input to the ECM through pins KNK1 and KNK2.