Circuit Description
WARNING: This page is about a different car, the 1997 GMC Pickup and 1997 Chevrolet Pickup. However, it is still accessible from the selected car via links, so may be relevant.
VCM utilizes knock sensors to detect engine detonation, allowing VCM to retard Ignition Control (IC) spark timing based on knock sensor signal received. Knock Sensor (KS) circuitry within sensor pulls down VCM-supplied 5-volt DC signal, so that under a no-knock condition signal on KS, circuit measures about 1.3 volts. Sensor produces an AC signal that rides on DC signal. Signal amplitude and frequency are dependent upon amount of knock experienced.
VCM contains a replaceable KS module. KS module contains circuitry that allows VCM to utilize KS signal and diagnose knock sensors and circuitry. VCM will set DTC if KS module is missing or faulty causing a continuous knock condition.