Knock Sensor: Description and Operation

Electronic Spark Control Circuit:

Purpose:
The Knock Sensor (KS) sends a signal to the powertrain control module (PCM) to retard ignition timing during spark knock conditions.


Operation:
The knock sensor is a piezoelectric device. A ceramic crystal vibrates with engine knock. The vibration of the crystal produces a voltage signal which is relayed to the control module where the signal is interpreted by the control module and used to calculate necessary ignition timing adjustments.

When the knock sensor senses no more knocking the PCM advances timing in small increments. This allows the control module to maintain maximum timing advance under various conditions.


Location:
The knock sensor is located in the engine block.