I just removed my knock sensor... 5 minutes and no blood yet...but something seems very strange with the harness connected to the sensor... Inside of the wiring harness connected to the sensor, the black wire just ends...and is not connected to the sensor, or anything else for that matter. (It is wrapped around the other wire, but not connected to it) What's the point of having two prongs on a sensor and two wires leading from the main harness to a sensor, but before the wires actually reach the sensor, one of the wires just ends, and there is only one wire attached to the sensor? Is this normal??

 

Yes, the two wire harness connector only has one lead actually going to the KS...weird, but hey, it's Nissan...

*shrug* That's just how it works.

 

The ground is chassis!

 

Correct that the ground is chassis. The black wire is not needed because the sensor does nothing but send a voltage signal when it senses vibration to the extent of pinging or knocking. This signal is a voltage change sent along the positive lead. Otherwise, the sensor simply resists within spec. Again, only when the sensor senses a knock does the resistance change, sending a voltage signal and activating the knock protection (retarded timing, etc) in the ECU.

 

You also need to be careful when removing the connector from your knock sensor. There's was a metal clip on my 95 maxima that needs to be pulled out which holds the connector to the sensor.

Typical resistance between pin 1 on the connector to ground is 550k ohms. And I think the resistance from pin 2 on the sensor (designated by white dot) to gound is the same.

 

Forgot to mention that measuring is done to the engine ground, which is two screws located at the center/bottom of the intake manifold.