A knob sensor is a knob-like vibration sensor in a vehicle’s engine that detects knocks in the engine. The sensor is a piezoelectric sensor that listens for knocks or detonation by detecting pressure.
A knock happens when the mixture of gas and air burns too fast or fails to burn smoothly. The knob sensor regulates the knock by sending a signal to the Electric Control Module, or ECM, which then delays the engine spark timing at certain intervals until the problem is resolved. The sensor monitors the engine’s performance and protects car parts such as the pistons, plugs, valves, rods and gaskets from the damaging effects of an engine knock.