Operation

The PCM contains integrated Knock Sensor (KS) diagnostic circuitry. The input signal from the knock sensor is 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 detects abnormal vibration (spark knocking) in the engine. The knock sensor is mounted in the engine block. The knock sensor produces an AC signal voltage under all engine operating conditions. During engine operation, the PCM calculates the average voltage of the knock sensor 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.