Question on Knock Sensor

[jjbarde]

Does anyone know where i can find the knock sensor on my 2003 Xterra 4WD SE. Also do u have any important advice on replacement? This is my first time messing with this.

[nissandoc]

its under the intake manifold. hard to see without a mirror. gotta remove intake to replace it. not a job for a beginner. the knock sensor sends a signal to the ecm to correct timing if it detects spark knock. some people differ on the importance of it, but for my money, i wouldnt bother with it. low on the totem pole of importance in my opinion.

[OffroadX]

Agreed, not worth the effort. It doesn't trip a code on its own and is not critical to normal operation. If you have a knock problem, address the cause to eliminate the knock, not the sensor that causes the engine to back off in response.

[jjbarde]

Thanks alot guys. That helps a lot.

[sweetwood]

I know I'm chiming in a little late but I had the same problem (and according to other forums it's very common) I pulled the positive lead off for a few minutes to reset the computer and when I reconnected it fixed the problem. Now it's running just like new. Hopefully this will help others in the future

[OffroadX]

Whatever might have changed by doing so had nothing at all to do with the knock sensor. It's either good or bad, and doesn't "fix" itself by disconnecting the battery. If you had a check-engine light, it wasn't the knock sensor responsible.
The knock sensor is pretty damn useless. If you have a supercharged Xterra, you need it to show "good" or your supercharger will never go out of bypass mode. On the non-supercharged ones the sensor does nothing unless you have knock, in which case you should fix the knock and not worry about the sensor.
I have the dyno numbers to prove that a bad sensor does not change the engine's behavoir one iota.

Brent

[rbuck282]

Are there any witing diagrams available...or better yet, photos?

I just had my water pump replaced and the knock sensor started throwing a code. I downloaded the pdf version of the shop manual, and honestly it isn't helping me at all, except that it says that it might be the wire or ground to the sensor that is the culprit. I CAN'T LOCATE THE WIRE!

Thanks in advance for any help!

[OffroadX]

You won't see the 2 wires for the sensor itself, but they go through the harness to the right of my fingertip:



The grounds you want to check are attached to the bolts on the bottom of the intake plenum behind the distributor.

Again, unless you're supercharged, the knock sensor is really not a concern at all and not worth the hassle of trying to make it happy.

[ejpolden]

I have an 02 Xterra with the Supercharger. When I start it up it has full HP. Step on the gas and she gets up and goes. After driving for about 15 minutes, all of a sudden, there's a significant loss of power. Step on the gas and it boggs down for a second and then gradually begins to pick up speed. The HP won't come back until it shut down and sits for a while. I took it to a local Nissan dealer and they ran tests for $100 and couldn't find anything wrong with it.Any idea what could be the cause of this? Could it be the Knock? Is there a difference between the Knock and the Knock Sensor?

[OffroadX]

If the knock sensor detects knock, or goes out, the system will put the SC in full-time bypass and de-tune the engine. This may be what's going on, particularly if you are not getting a check-engine light when it happens since the knock sensor won't trip the light.

[ray toepfert]

Originally Posted by ejpolden

I have an 02 Xterra with the Supercharger. When I start it up it has full HP. Step on the gas and she gets up and goes. After driving for about 15 minutes, all of a sudden, there's a significant loss of power. Step on the gas and it boggs down for a second and then gradually begins to pick up speed. The HP won't come back until it shut down and sits for a while. I took it to a local Nissan dealer and they ran tests for $100 and couldn't find anything wrong with it.Any idea what could be the cause of this? Could it be the Knock? Is there a difference between the Knock and the Knock Sensor?

I had the same problem. Ended up having to replace the knock sensor, made a huge difference in power and gas mileage. Replaced mine myself, not sure how good of a mechanic you are but it is not a easy or quick job to do. You could expect to pay betwwen $650-$1000 depending where you live. If you have questions please feel free to email me [email protected]