The knock sensor is a device located on an engine that senses irregular vibrations. "Pinging," or engine knock, is a result of premature gasoline detonation within the combustion chamber of the engine. When a knock is detected by the knock sensor, the information is sent to the car's computer, which may adjust the timing or the air fuel mix to stop the knocking sound. Depending on the make and model of your vehicle, the knock sensor(s) may be located in the intake manifold, engine block or cylinder head.
Park your vehicle on a level surface and open the hood.
Extend the auto inspection mirror and hold the mirror under the intake manifold. The intake manifold is located where the exhaust pipes connect to the engine. The knock sensor is round, about two inches in diameter and screws into the engine block near the intake manifold. A wiring harness comes out of the top.
Look on both sides of the intake manifold. Depending on the engine, you will have one or two knock sensors. V-6, V-8 and V-10 engines typically have two knock sensors. Inspect the area with a flashlight if you are unable to find the knock sensor(s).
Obtain a service manual if the knock sensor is not located near the intake manifold. If the knock sensor is inside the engine, you will need to drain the antifreeze.
