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 to the ESC controller or the MEM-CAL portion of the ECM (on models equipped with 4L80-E transmission). The ECM then retards ignition timing until the engine knock ceases. Two knock sensors are used on 4.3L CPI engines.

For additional information on knock sensor operation, see ESC DETONATION RETARD OPERATION under IGNITION TIMING CONTROL SYSTEMS (GASOLINE).

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 the suspected cause of a driveability problem, perform functional check of ESC system. See I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.