Knock Sensor: Description and Operation

Detonation (Knock) Sensor Circuit:

Sensor Operation
The knock sensor is a piezo-electric type crystal which converts knocking vibrations into A/C electric signals.

Location
It is installed on the engine block, below the cylinder head, under the intake manifold.

Operation
If engine knocking occurs, the crystal shakes causing an A/C voltage to be produced. When engine knocking is detected by the ECM, it retards the timing to reduce the incidence. Some reduction in engine power will be noticed with the reduction in timing.

Knock Sensor:

Construction
The sensor is made of three elements: Titanium Oxide, Zirconium Oxide and Lead.