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.
NOTE:
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 this section.