Operation

The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. Input signals from the knock sensors are used to detect engine detonation, allowing the PCM to retard Ignition Control (IC) spark timing based on the amplitude and frequency of the KS signal being received.

The knock sensor(s) detect abnormal vibration (spark knocking) in the engine. The knock sensor(s) are mounted in the engine block near the cylinders. The knock sensor(s) produce an AC signal voltage under all engine operating conditions. During engine operation, the PCM calculates the average voltage of each knock sensor's signal. If the knock sensor system is operating normally, the PCM should monitor KS signal voltage varying over 0.5 volt above and below the calculated average voltage.