Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Knock Sensor (KS)
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.
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.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.