Knock Sensor

Knock Sensor:

The knock sensors in the vehicle serve to detect abnormal vibration (spark knocking). There is a knock sensor on each of the two cylinder banks. Engine vibration causes the piezo-electric device within the knock sensor to send an AC signal to the ECM. The ECM will retard timing to a maximum correction based on the signal. The ECM is capable of detecting too much noise and too little noise. A noise level reading is taken at idle and used as a reference reading. There is a time frame around the TDC combustion event when the knock sensor signal is considered by the ECM.