Knock Sensor

The knock sensor is a piezoelectric device which detects abnormal engine vibrations (spark knock) in the engine. This vibration results in the production of a very low AC signal which is sent from the knock sensor back to knock sensor module, if equipped (mounted on PCM), or to the EEPROM/PROM portion of PCM on models not equipped with a knock senor module. The PCM will then retard spark timing until engine knock ceases. Some models use 2 knock sensors.

For additional information on knock sensor operation, see IGNITION TIMING SYSTEMS  under IGNITION SYSTEM. Failure in knock sensor circuit should set a related Diagnostic Trouble Code (DTC). If a related DTC is not present and knock sensor system is suspected as the cause of a driveability problem, perform a functional check of the knock sensor. See appropriate SYSTEM & COMPONENT TESTING article.