Knock Sensor: Description and Operation

Purpose
Knock sensor detects engine knock and sends a signal to powertrain control module engine (PCME). When knocking occurs, PCME retards ignition timing until knock ceases.

Operation
When sensor crystal structure is distorted by a knock of sufficient intensity and frequency, a small voltage potential is created. Voltage signal is interpreted by PCME as engine knock and timing is retarded as needed until knock is eliminated.

Construction
Knock sensor contains a crystal element with electrodes attached to opposing sides.