Knock Sensor: Description and Operation

PURPOSE
The knock sensor is an electronic sensor that senses engine 'knock' or detonation and reports to the Engine Control Module (ECM). The sensor input is used to determine proper ignition and injection timing.

OPERATION
When the knock sensor detects engine detonation, the piezoelectric element resonates at the same frequency and produces a voltage that varies according to the amplitude of the knock.

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