Knock Sensor: Description and Operation

SPARK KNOCK
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.

DESCRIPTION
To control spark knock a Knock Sensor (KS) is used. This system is designed to retard spark timing to reduce spark knock in the engine. This allows the engine to use maximum spark advance to improve driveability and to improve fuel economy.

The Knock Sensor system has two major components:

^ The KS module.

^ The Knock Sensor.

OPERATION
The knock sensor is mounted into the engine block under the intake manifold. The knock sensor produces an AC voltage which increases with the severity of the knock. This signal voltage inputs to the Powertrain Control Module (PCM). The PCM then adjusts the Ignition Control (IC) to reduce spark knocking.