Knock Sensor: Description and Operation

Electronic Spark Control Circuit:

Knock Sensor (KS) Sensor:

PURPOSE
Varying octane levels in today's gasoline can cause detonation (also known as spark knock) in an engine.
The Knock Sensor (KS) system has a knock sensor that are used on 4.3L engines. The KS system reduces spark knock (detonation) in the engine. This allows the engine to have a maximum spark advance for improved driveability and fuel economy.

CONSTRUCTION
This KS system has three main components:
- KS Module.
- Knock sensor
- Control Module

OPERATION
The knock sensor detects abnormal vibration (spark knocking) in the engine. The knock sensor is mounted in the engine block near the cylinders. The KS module receives the knock sensor information and sends a signal to the ECM. The ECM then adjusts the Ignition Control (IC) to reduce spark knocking.
The KS module sends a voltage signal (8 to 10 volts) to the ECM when no spark knocking is detected by the knock sensor. This allows the ECM to maintain maximum timing advance under various engine load conditions. When the knock sensor detects spark knock, the module turns "OFF" the circuit to the ECM. The ECM then retards IC to reduce spark knock.