Circuit Description

PCM uses Knock Sensor (KS) to detect engine detonation. KS produces an AC signal at all engine speeds and loads. PCM makes adjustments to spark timing based on amplitude and frequency of KS signal. PCM checks the KS system by comparing actual KS signal to noise channel. A normal KS signal should switch outside of voltage range greater than or less than noise channel. DTC will set when engine is running and PCM detects a malfunction in the KS diagnostic circuitry that will not allow proper diagnosis of the KS system.