Knock Sensor

The PCM uses a Knock Sensor (KS) to detect abnormal vibration in the engine (detonation/spark knocking). The knock sensor is mounted in the engine block, under the intake manifold. The knock sensor produces an AC signal at all engine speeds and loads. The PCM then adjusts the spark timing based on the amplitude and frequency of the KS signal.

A knock sensor module is no longer used to diagnose the knock sensor system. The circuitry is integrated into the PCM. The PCM uses the knock sensor to determine the amount of normal engine noise (noise channel) for a wide range of engine speeds and loads. The PCM compares the actual knock sensor signal to the learned noise channel.