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Knock Sensor QuickFix

The knock sensor is used by the ECM to fine tune ignition timing. A faulty knock sensor will cause a faulty code to set, and may also cause ignition timing to be skewed. Lack of power may also be another symptom. These are the knock sensor facts.

1) The knock sensor is a type of microphone, screwed to the engine block or manifold.
2) It is a piezo electric or crystal component.
3) Knock sensors produce their own electricity.
4) A knock sensor produces alternating or AC current.
5) The sensor is tuned to between 6 to 9 thousand Hertz, which is the pinging frequency, so as not to confuse the ECM.
6) There are two types of knock sensors, the older wide band, and the newer resonant or tuned knock sensor.
7) You test these two types of sensors differently.
8) To test the wide band knock sensor, with engine and key off, probe with a volt meter set to AC, between battery ground and the knock sensor signal wire. Then, light tap near the knock sensor using an extension or back of the ratchet wrench.
9) The resonant newer style knock sensor will not react to engine tap. These sensors are tuned only to an engine ping.
10) To test these sensors, connect the volt meter as before, start the engine, then remove the fuel pump relay or fuse. As the vehicle is starved for fuel, preload the engine a bit by putting the car in gear, foot on brake, and accelerate a bit. The fuel starved engine will ping.

On both tests you should see an AC voltage outputted. That concludes the knock sensor QuickFix.