Hyundai Excel Knock Sensor

Your engine's knock sensor picks up evidence of pre-ignition, pre-detitanation or spark knocking in your engine. Knocking refers to a pocket of air/fuel mixture that ignites ahead of the ignition from the spark plug, meaning it has ignited in the wrong part of the engine cycle creating a very noticeable increase in cylinder pressure. If knocking is detected, the signal from the sensor will indicate to the ECU that the timing needs to be altered until the knock has been eliminated.