Knock Sensor (KS)

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

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 (3.1L, and some "C" and "K" series with 4.3L, 5.0L and 5.7L) or the PCM (all others). The PCM then retards ignition timing until the engine knock ceases. Two knock sensors are used on all "S" and "T" series with 4.3L engine and some "C" and "K" series with 4.3L engine.

NOTE: For additional information on knock sensor operation, see ESC DETONATION RETARD OPERATION under IGNITION TIMING CONTROL SYSTEMS.

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 SYSTEM/COMPONENT TESTS - GASOLINE article in the ENGINE PERFORMANCE section.