The knock sensor (KS) system enables the engine control module (ECM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation. The KS is located on the intake side of the engine block. The KS produces an AC voltage signal that varies depending on the vibration level during engine operation. The ECM adjusts the spark timing based on the amplitude and the frequency of the KS signal. The ECM receives the KS signal through a signal circuit. The KS ground is supplied by the ECM through a low reference circuit. The ECM learns a minimum KS noise level at idle and uses calibrated values for the rest of the RPM range. The ECM should monitor a normal KS signal within the noise channel. When the ECM detects a KS signal that varies outside of the noise channel, the ECM will retard the spark timing until the knock goes away. If the ECM is operating on large amounts of spark retard and is unable to eliminate the knock, DTC P0326 will set.

The engine is running.