# HOW TO: Relocate the Knock Sensor on the X-trail



## thetimster (May 6, 2005)

Well, I finally tried it and did the knock sensor relocation today. Again, as posted many times by ValBoo and many others, doing so CAN lead to unsensed knocks and potentially damage to the engine. The chance of knocks happening will theoretically be less by using gas higher than 91 octane... something I have always used anyway and will now definitely continue to do so. Also, the KS on the 04 X-trail onwards are not as sensitive as the 02 and 03 models and thus usually don't need to be relocated.

Again, my reference came from: http://www.nissanperformancemag.com/december02/knock_sensor/ and from reading many posts about it.

Reading the KS relocation accounts of the Sentra, I was fooled into thinking this would be easy. And it is not!!! The KS on the X-trail is not as accessible. In the accounts from the Sentra SE-R and Spec-V, all you needed to do to get to the KS is the turn the wheels hard left. But despite doing that, I could not do so on the X.

So anyway, here is my account:

1.) I disconnected the negative terminal of the battery as recommended.
2.) After I realized I couldn't get to the KS without doing so, I removed my right front tire (passenger side for us) and set up the vehicle on a jackstand. After doing that, this is what you will see. The KS can be seen by peeping upwards through the small gap behind the suspension. It is difficult to get to it through the gap so the splash guard had to be removed by removing the clips and bolts holding it in place. There are other clips and bolts on the undersurface which are shown in the second picture. Once these are removed, the splashguard comes off easily.


3.) You'll see this after the splash guard comes off. I already see the pulley I'll be replacing when my UR pulley arrives. But that'll be another post. Again, follow the arrow and you'll see the KS sitting so tantalizingly close, but at the same time seemingly so inaccessible.

4.) The bolt IS 12mm. I found it difficult to use a regular wrench and had to use an offset 12mm wrench. With a light shining and at the same time looking from behind the suspension, I reached in with my wrench in my right hand through the gap in front of the suspension to undo the bolt on the KS. (See picture below.) 

5.) Once the bolt was loosened, it was very difficult to continue to undo the already loose bolt with the wrench. It became easier to sit inside the fender well, face the front of the car and reach in blindly with my left hand through the gap in front of the suspension and twist the bolt off that way. It is difficult to remove the KS from its harness with one hand. I ended up doing so by sitting facing the suspension and reaching inside with both hands (left hand through the rear gap and right hand through the front gap) and undoing the harness that way. I'm sorry I forgot to take a picture of the KS while it was on. But this is the place where it was. This picture was taken by looking upwards and forwards through the gap from behind the suspension.

This is what the sensor looks like. Sorry for the blurry pictures. They looked ok on the LCD camera screen. These were also taken after the ground wire was already attached.


6.) Attaching the ground wire is simple. I took a new nut and bolt and ran it through a couple of washers, the KS and the ground wire and tightened it. Some posts detail placing foam or other dampening material before wrapping it in electric tape. But the NPM article didn't so I didn't do so either. This is what it looked like afterwards.

7.) I had a very difficult time looking for some place to ground the wire. The Xtrail doesn't have the gold bracket that the Spec V articles and posts talk about. And all the other nearby bolts were VERY tight (which is good I guess). They are also difficult to apply torque to since they are all quite deep. So in the end I decided to ground the wire back from where the original KS came from and with the original bolt with some washers. It was more difficult to tighten the bolt than remove it. In the end I did it by once again sitting facing the suspension and reaching inside with 2 hands. The left hand braced the wrench against the bolt while the right hand twisted the bolt tight. This is what it looked like afterwards.

8.) Next the KS itself needed to be tied someplace else. It was also difficult to find someplace to tie it. But if you look in the direction of the arrow in this picture...

... you will see a harness to which the KS can be ziptied as seen in the next picture.

9.) After that its easy... replace the splash guard, put the tire back on, take the car of the jack stands and reattach the battery.

Now that I know how to do it, I could've probably done the whole thing in about 1.5 hours. It would also help if the ground wire was prepared beforehand. As it turns out, it took me more than 3 hours to do the whole thing. Most of the struggle was to get to the KS without first removing the tire, then later without removing the splash guard.

Also, watch out for these edges. My arms got inadvertently and repeatedly scratched and nicked while reaching inside.  


I took the X out after this and initial driving impression is a slight increase in low end pick-up even though I wasn't expecting anything since they say that it takes a couple of days for the ECU to get used to any mod. I guess if engine vibration was previously sensed as knocks then I could potentially get more immediate power now. I didn't push the engine hard... despite using high octane gas I was just slightly nervous about getting knocks. But as I gradually increased the RPM's, there wasn't any perceptible problem. So, so far so good. I will keep you guys posted if any issues come up. I hope this post is helpful to those who plan to do this. I find the pictures from other posts slightly lacking in detail. And so far, I have not seen any posts for the X-trail. If there is any part that is unclear or i could've done wrong, differently or better, please let me know.

One thing that other posts mentioned that might be tried is to get a new KS then grounding and using that... all the while keeping the old KS in place so the mod can be easily reversed. I don't have access to a spare KS here. So unfortunately that wasn't a reasonable option right off the bat. 

Well, any feedback would be appreciated! Happy X-ing everyone!


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## Sergei_dekker (Jun 4, 2005)

I don;t really understand the pics man...esp the part on how u put it back with all the duct tape attatched to it....and does the knock sensor come with wires beforehand thats attatched???


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## thetimster (May 6, 2005)

Sergei, which particular pics are you having trouble with... I'll try to be more clear if you can tell me which ones are unclear.

When I put it back, it is electrical tape covering it, not duct tape. And since the KS has to be relocated, you have to find a place to secure it. 

The KS is originally attached to a harness. You need to reattach the KS to the harness before securing it someplace else. The KS also needs to be grounded. So you will need another wire and crimp 2 terminals on each end of it. One end will be attached to the KS, the other to a ground. 

The basic principle including the tools you will need are in the website I referenced to. I placed the reference there particularly so I wouldn't need to go through those again.

Let me know how else I can help.


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## ValBoo (May 19, 2003)

Very nice post!

good tips and good pictures overall.


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## kmccann (Jan 5, 2005)

Thats a great post! Thanks man!


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## Sergei_dekker (Jun 4, 2005)

thetimster said:


> Sergei, which particular pics are you having trouble with... I'll try to be more clear if you can tell me which ones are unclear.
> 
> When I put it back, it is electrical tape covering it, not duct tape. And since the KS has to be relocated, you have to find a place to secure it.
> 
> ...



So basically the KS that u have shown in the pic already has been attatched with a ground wire??? what hapapens to the original wire that was connected to the KS? now i have fig. it out that u have to remove the KS...put a screw with many washers and a ground wire attatched to it which Links to the KS and reconnect the KS to the harness??


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## thetimster (May 6, 2005)

Sergei_dekker said:


> So basically the KS that u have shown in the pic already has been attatched with a ground wire??? what hapapens to the original wire that was connected to the KS? now i have fig. it out that u have to remove the KS...put a screw with many washers and a ground wire attatched to it which Links to the KS and reconnect the KS to the harness??


Sergei, to answer your questions...

Yes, the picture shown ALREADY has the ground wire attached to it. It's basically the black wire coming out towards the left side of the KS. Otherwise, the thick black thing with the bolt through it is the KS.

The original wire attached to the KS is a harness. It slips into and clips onto the KS. In the end, all you do is take out the KS, move it someplace else, then attach a ground wire to it, then attach the ground wire to another site... basically any place you can ground it to. You can make a LONG wire and ground it above the engine if you want. But that runs the risk of the wire coming in contact with some moving parts. So its best to keep it short and in the general vicinity of the original location where there already are some harnesses in place. Since it is difficult to attach the ground wire to the KS without first taking it off the harness, that is what most people have done. I know I wouldn't have been able to attach the ground wire to the KS without taking it out.

Hope this helps!!


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## Sergei_dekker (Jun 4, 2005)

okay so if u ground the KS...what about the original wire connected to the KS? Ziptie it to something??? then just replace the KS back with the groundwire grounded to something??


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## thetimster (May 6, 2005)

Sergei_dekker said:


> okay so if u ground the KS...what about the original wire connected to the KS? Ziptie it to something??? then just replace the KS back with the groundwire grounded to something??


The original wire is IN the harness that the KS is originally attached to. So it is still attached to the KS after you are done. All that is really done is relocating the KS with its original wire/harness to another (more quiet and less vibrations) spot by securing it with zipties, and attach a ground wire of which one end is attached to the KS and the other to a ground.


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## Sergei_dekker (Jun 4, 2005)

thetimster said:


> The original wire is IN the harness that the KS is originally attached to. So it is still attached to the KS after you are done. All that is really done is relocating the KS with its original wire/harness to another (more quiet and less vibrations) spot by securing it with zipties, and attach a ground wire of which one end is attached to the KS and the other to a ground.


 but then what do u do with the old spot where the sensor is? seems like u used washers and a screw and connected the ground wire there...is that correct? sorry for asking so many qns....i need to get this clear before i even dare to try it...which is why i never installed the BSR kit....no one here in my country is qualified to do that and my nissan mechs didnt want to take the risk cos they are not trained


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## thetimster (May 6, 2005)

Yes, the ground wire was placed where the KS previously was. I used the same bolt that was there before. If you do, you have to put washers because the bolt will not go all the way in. You have to approximate the thickness of the KS with the washers. I couldn't find any other ground location. If you do, you might not need to put it back to where the KS originally was.

The BS removal cannot be reversed... unlike the KS relocation. So yes... I wouldn't do that unless you are willing to drive around without a warranty. I am now going on 3 years so my warranty will be out soon and I plan to do it after that. The BSR is a MUCH more difficult mod. KS relocation only took others half an hour. The fastest BSR I've seen posted is 1.5 hours with most extending to 3. For me, it might take the whole weekend!  

No problems about the questions. It took me a lot of reading and asking to know how to do it as well. Good luck!


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## Sergei_dekker (Jun 4, 2005)

my warranty has long expired as my car is already 3 yeras old...my BSR kit is now sitting in a drawer collecting dust...cos unlike the KS if u have some foul-ups its not that bad but for the BS if there is a foul-up then its just as good as sending it to the workshop for expensive repairs..which is why i ddi not have the guts to even try....oh yea when u remove the tyre and fix it back later after relocating the KS...will the wheel alignment be out???I do not want to have a vibrating steering wheel again


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## thetimster (May 6, 2005)

Alignment should be OK since you aren't doing anything with the suspension.


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