DTC P0327: Knock Sensor Circuit: Description

WARNING: This page is about a different car, the 2002 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Knock Sensor (KS) is a piezoelectric device that produces an AC voltage of different amplitude and frequency based on engine mechanical vibration. Amplitude and frequency are dependent on level of knock sensor detects. ECM learns an average noise level from knock sensor (based on calibrated average) and monitors signal to verify that it stays more than a minimum value. Knock sensor signal is only used during top dead center combustion event of firing cylinder. When in a combustion event, ECM filters knock signal and compares it to normal calibration noise level for that RPM. If ECM has determined that knock is present during combustion event, it will retard timing on next firing cylinders until knock is eliminated. ECM will always try to work back to zero compensation level or no spark retard. DTC sets when ECM has detected no normal knock sensor voltage activity.