Knock sensor harness plug question

Post by **Oldyeller** » Sun Aug 11, 2013 2:28 pm

I did the knock sensor relocate on my 02 Xterra this morning using the original harness and connector as opposed to splicing in the Maxima sub harness. I was able to gain access to the knock sensor through the front while replacing the timing belt and water pump, I took a 2 foot pry bar and placed the tip of it on the connector, gave it a whack and off it came. I was then able to simply pull the harness out from the rear of the motor. I figure this was better than splicing into the harness. Anyhow, I do have a question... There is only 1 wire going into the harness connector, is this normal? I peeled back the loom and it looks like the mesh shielding ends about 3 inches before the connector and is taped off.
The sensor has 2 pins so why is there only 1 wire going to it?

Post by **Morpheus** » Sun Aug 11, 2013 8:16 pm

There should be 2 wires in the harness and the plug. 1 is signal, the other is ground.

Post by **Oldyeller** » Sun Aug 11, 2013 8:54 pm

Morpheus wrote:There should be 2 wires in the harness and the plug. 1 is signal, the other is ground.

That's what I thought but the only wire in the loom is a coax type with the center wire going to the sensor connector and the mesh shield just ends and is taped off. I have a buddy who is a very advanced Nissan technician and he said that the knock sensor is a piezoelectric device that makes it's own electric signal that is transmitted to the ECU via the 1 wire.
Does that make sense to you?
I cant say for sure but the harness looks to be factory i.e. it doesn't look like its been tampered with.

Post by **Lukexskywalker** » Sun Aug 11, 2013 9:00 pm

I think there is only one wire into the knock sensor connector. The one wire is a voltage wire and the sensor grounds on what it is bolted to. I have seen 5 first gen knock sensors and all had only one wire.

Post by **Morpheus** » Sun Aug 11, 2013 10:24 pm

No, you're right. I was remembering wrong.

The sensor grounds its self through the bolt, and the harness is a one wire signal, however somewhere i remember reading that someone cut an old sensor open and found that 2nd pin was an internal ground.

When I did my bypass I used a 2 wire harness connector and put that pin to the ground circuit in the same harness.

Has worked fine for me since doing the bypass.

That's where I remembered the ground thing from.

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