Knock Sensor (Except 2.5L)

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. Controller normally applies a 12-volt signal to terminal B7 at the ECM. ECM interprets this as a "no knock" condition. When controller receives a knock signal from the knock sensor, controller will remove the 12-volt signal from the ECM monitored knock signal line. ECM will then retard ignition timing until the engine knock ceases (12-volt signal is returned by the controller). 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. See SYSTEM/COMP TESTS article.