Knock Sensor (KS) System Description: Operation

The knock sensor system has 2 major components.

• The knock sensor
• The KS module circuitry located inside of the PCM

The KS detects detonation in the engine. The KS is located in the center of the engine block below the intake manifold. The KS module receives the KS signal and communicates within the PCM. After the correct calculations are made the PCM adjusts the ignition timing in order to reduce the detonation.

When the KS detects detonation, the KS module opens a circuit in the PCM. In response the PCM retards the spark advance in order to reduce the detonation. The amount of timing retard that the PCM applies is based on the engine speed and the length of time that the engine detonation is detected. Once the spark timing is retarded, the KS module performs calculations in order to determine whether more or less spark timing advance is required. Normally the ignition timing advance is increased until zero retard, or normal ignition timing, is re-established. If detonation occurs again the whole cycle will repeat. The alteration of the ignition timing by the KS often occurs continuously while the engine is running even though no detonation is heard by the vehicle's operator.