Sunfire L4-2.2L VIN 4 (1996)
Knock Sensor: Description and Operation
DESCRIPTION
Varying octane levels in the gasoline can cause a detonation in performance engines. Detonation is sometimes called a spark knock. A spark knock
causes the pistons and the rings to vibrate and rattle, sometimes producing a knocking sound.
In order to control a spark knock, a Knock Sensor (KS) is used. This system is designed to retard the spark timing up to 15 degrees in order to
reduce a spark knock in the engine. This allows the engine to use a maximum spark advance in order to improve driveability and fuel economy.
OPERATION
The Knock Sensor (KS) system has two major components:
1. The KS module.
2. The Knock Sensor (KS).
The Knock Sensor (KS) detects abnormal vibration (spark knocking) in the engine. The sensor is mounted in the engine block near the cylinders.
The sensor produces an AC output voltage which increases with the severity of the knock. This signal voltage is sent to the Powertrain Control
Module (PCM). The PCM then adjusts the Ignition Control (IC) timing to reduce the spark knock.
A fault in the KS circuit or module will set a DTC P0325. Refer to System Diagnostic Table: Knock Sensor System Diagnosis for more
information. See: Computers and Control Systems/Testing and Inspection
