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 back to the ECM controller or to the MEM-CAL portion of the ECM. The ECM will then retard ignition timing until the engine knock ceases. A fault in the ESC circuit should set a Code 43. When Code 43 is not present and the ESC system is suspected as the cause of a driveability problem, see appropriate CHART C5 for that system for additional diagnostic information.