Knock Sensor: Description and Operation

PURPOSE
The knock sensor senses engine detonation and reports to the ECU. The sensor input is used to determine proper ignition and injection timing.

LOCATION
Mounted to the engine block under the intake manifold.

CONSTRUCTION
The 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 the input signal to the ECU.