Facet Ignition Knock (Detonation) Sensor | 13627566786

Knock sensors monitor the pre-detonation of the air-fuel mixture in an internal combustion engine. Pre-detonation occurs when part of the air-fuel mixture ignites before normal combustion creating a shockwave that resonates through the engine block that emits an audible knocking or pining sound. When the knock sensor detects the knock or ping, it relays that information to the engine computer so the computer can adjust engine timing and the amount of fuel entering the engine to stop the pre-detonation. Prolonged pre-detonation in one or more cylinders can damage the cylinder walls, pistons, cylinder head gasket, cylinder head, spark plugs, and engine valves.

When a knock sensor detects engine knock for a prolonged timeframe, the engine computer in your BMW will illuminate the check engine light with a fault code indicating excessive engine knocking that can not be stopped by adjusting timing and fuel entering the engine. Excessive engine pressure due to carbon build-up in a cylinder, excessive engine load, an improperly timed engine, and lower than recommended octane fuel can all cause excessive knocking that the engine computer can not adjust for.

Knock sensors are mounted directly to the exterior of the engine block to pick up the vibrations created by pre-detonation. However, due to their location, they can often be challenging to access and may require extensive removal of components such as intake or exhaust manifolds to replace. With that in mind, on average, knock sensors can take between 20 minutes to up to four hours to replace.

View more BMW Knock Sensors.