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. Some models use 2 knock sensors.

For additional information on knock sensor operation, see ESC DETONATION RETARD OPERATION under IGNITION TIMING SYSTEMS  under IGNITION SYSTEM. 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 a functional check of the ESC system. See I - SYS/COMP TESTS article in this section.