Knock Sensor Module: Description and Operation

Description
Varying octane levels in gasoline can cause detonation in high performance engines. Detonation is sometimes called spark knock. Spark knock causes the pistons and rings to vibrate and rattle producing the spark knocking sound.
To control spark knock a Knock Sensor (KS) is used. This system is designed to retard spark timing up to 15° to reduce spark knock in the engine. This allows the engine to use maximum spark advance to improve driveability and to improve fuel economy.

Operation
The Knock Sensor system has two major components:
- The KS module
- The knock Sensor
The knock sensor is mounted into the back of the engine block. The knock sensor produces an AC voltage which increases with the severity of the knock. This signal voltage is then sent to the Powertrain Control Module (PCM). The PCM then adjusts the Ignition Control (IC) timing to reduce spark knocking.