Thanks a million for your knock sensor write-up. I went through the whole thing, and I only have one question:

The knock sensor has 2 terminals. But the harness that came off of mine (and the one in your picture), only has one.

I had to make my own harness out of one that Kaleb sold me. It had a ground. The original harness had a ground at the top connnector, but it was wrapped around the signal wire, and terminated before the sensor, and did not have a terminal that connected to the sensor.

What I did was plugged it up anyway, with a disconnetable connector so I could take it off if it didn't need a ground. Is this okay?

Thanks,

I know that you were going to add pictures to your write up, but I don't know if you have done that yet. I took a few (very few), but if you'd like them, let me know, and I'll email them to you.

Thanks,
Jayson

 

The sensor itself has two terminals on it. The wiring harness that attaches to it at the sensor has one wire connection. Further up that wiring harness is another connector (which is visibile in the engine bay for checking the knock sensor). This connector does indeed have two wires in the connector. So what's the deal?

First, remember how a knock sensor works. It doesn't quite 'listen' for engine knocking, it senses it through pressure spikes. This is why you don't want to jar or drop one of these sensors. The sensor is located on a flat spot of the engine block. The sensor then converts these pressure spikes (knocking) into a voltage through the piezoelectric element. It then sends the voltage to the ECU for evaluation.

Now, on the 3rd gen knock sensors (both VG and VE), the wiring harness confuses some people. There actually are two wires that lead to the knock sensor. One is for the ECU voltage and another is a shielded ground wire. At all times except for the check connector, the shield ground is wrapped around the insulation of the voltage wire, and then electrical tape is tightly wrapped around that. The entire wire from the ECU to the knock sensor is like this except at three places... at the ECU, at the knock sensor, and at the middle check connector. At the ECU, the wire is grounded out to the chassis (FSM shoes an engine ground). The connector has two wires because the shield splits into a normal wire a few inches on either side of the connector, just so it can be connected. Then, a few inches from the actual knock sensor, the shielded portion of the wire stops.

This shielding is probably to prevent errant voltages from creeping into the ECU wire so the ECU gets a steady signal. Now, why does the knock sensor have two terminals? I don't know. Perhaps this model knock sensor is used in other OEM applications like on a Toyota for example, and they wire it up differently. Remember Nissan doesn't make all their engine sensors, they source them out to different OEM parts manufacturers.

Short question, big answer. Make sense now?

 

YEah. one more question though, your write-up says disconnect to battery for 12 hours or so to reset the ECU, but the job took me 2 days to do and the battery was disconnected the whole time. DO I need to reset again?

 

Nope, that should be good. Notice any differences? If not then maybe try unplugging it overnight again.

 

I have noticed a difference, but it might be the weather. It's warm again today, so we'll see.

Do you need my pictures? Like I said, I took a few.

 

Nope, I got the writeup all ready to go, they just have to put it up at 4dsc.com (been waiting a week)

 

psst. here is a pic of the little guy.
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Project VE: The Teardown!



MrGone