A car knock sensor is located on the intake manifold, cylinder, or engine block. The purpose of the knock sensor is to sense unusual pulsations caused by the engine detonation. A bad knock sensor will not let the engine accelerate properly while driving on the highway, and cause the vehicle to lose fuel mileage.

There are, however, some other factors that can cause excessive engine knock – when the ECU cannot compensate for the combustion anomalies within the combustion chamber – or that can cause the sensor to fail completely.

Heat
Although engine knock happens quite often, an excessively hot day can cause an excessive amount of knock. Even the hottest days cannot usually create enough abnormal knocking to make the ECU unable to adjust timing and compensate. But, an already bad knock sensor can work with the heat to exacerbate the knocking issue.
Bad Fuel
Bad fuel is usually not a big concern for most drivers, but it happens enough that it can cause excessive knocking. Like excessive heat, it is not usually the cause of knock sensor failure, but it could cause enough abnormal knocking for the ECU to fail to delay timing enough and mitigate it adequately.

Faulty Spark Plugs
Faulty and clogged spark plugs are the causes of many different issues, including abnormal engine knock, and if persistent enough, knock sensor failure.

Carbon Buildup
Any kind of accretion or buildup is the bane of any sensor since it relies on the information it uses from the environment in which it resides. Carbon buildup is a common cause of sensor failure, especially if it is located in the engine block. Some knock sensors are located on the intake manifold which lessens the chances that it suffers from carbon buildup, but a bad or poorly maintained air filter can let in dust particles that can essentially do the same thing.

There are various types of Knock Sensor, they vary by vehicle make and model and are located or mounted at the engine.

Your engine knock sensor manages combustion timing in your engine, sending information to your vehicle’s ECU so that it can make minuscule ignition adjustments to keep your engine running correctly. A bad knock sensor will exhibit an abnormal knocking or pinging noise, prevent normal acceleration, reduce fuel economy, and cause the check engine light to illuminate. If you experience any of these issues, you should visit a local mechanic to have them diagnosed.