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 the ESC controller, or to the MEM-CAL portion of the ECM on models not equipped with a controller. The ECM will then retard ignition timing until the engine knock ceases.

For additional information on knock sensor operation, see ESC DETONATION RETARD OPERATION within IGNITION TIMING SYSTEMS under the IGNITION SYSTEMS heading in this article.

A fault in the ESC circuit may set a related trouble code. When a related trouble code is not present and the ESC system is suspected as the cause of a driveability problem, perform functional check of ESC system. Refer to SYSTEM/COMPONENT TESTS article in this section.