Knock Sensor: Description and Operation

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.

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

OPERATION

Knock Sensors Circuit:

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 the input signal to the ECM. This signal is input to the ECM through pins KNK1 and KNK2.