Knock Sensor

What Does a Knock Sensor Do?

The knock sensor monitors engine vibrations caused by detonation in internal combustion engines, and detects abnormal combustion events caused by engine detonation, commonly called engine knock. Located on the engine block or cylinder head, the knock sensor sends signals to the engine control module (ECM) when the fuel/air mixture detonates prematurely. Premature ignition, detonation, or knock can be caused by a variety of factors, including a lean air-fuel mixture, timing issues, or low-octane gasoline allowing combustion to occur before the spark plug fires in the cylinder. If the knock sensor sends signals indicating detonation to the ECM, it can then adjust the timing of the ignition spark, the fuel injection, or the air/fuel ratio to help prevent knocking. If the knock sensor is not functioning correctly, then the vehicle may experience poor fuel economy, loss of acceleration and performance, or engine noises similar to a knock, ping, or thumping sound. If left unrepaired, engine knocking can cause damage to the engine, and may require costly engine service or component replacement. When you need to fix engine knock, get your Check Engine light tested for free, or replace your knock sensor, O'Reilly Auto Parts offers knock sensor replacements and resources for most vehicles. You can also check out our article about what causes engine knock to learn more about engine detonation.