DTC P0326: Knock Sensor Performance: Description

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. PCM 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, PCM filters knock signal and compares it to normal calibration noise level for that RPM. If PCM has determined that knock is present during combustion event, it will retard timing on next firing cylinders until knock is eliminated. PCM will always try to work back to zero compensation level or no spark retard. DTC sets when PCM cannot eliminate spark knock by retarding spark timing which is most likely caused by engine noise.