Nissan XTerra Forum banner

1 - 20 of 110 Posts

·
Premium Member
Joined
·
698 Posts
Discussion Starter #1 (Edited)
Hello everyone, Jackal here. I have put together another how-to. This time, I wanted to improve upon the knowledge in the Xterra (and I suppose Frontier) community about the knock sensor resistor mod. First, let me be clear this how-to is my own work on my own vehicle. IF you choose to perform this on your own vehicle you do so at your own risk. Secondly, I did not invent the resistor mod, I have merely put this together to make it easier for X drivers to know what is involved. With that in mind, there is some reading involved but that is meant to clarify the obvious and no-so-obvious things.

(For further info on knock sensor resistor mod click here. Or click here for the knock sensor relocation mod.)

LET'S GET STARTED!

SUPPLIES:
3/4” flex loom tubing cut to about 5 inches.
Electrical tape
Silicon sealant
Camera to take pics
2 x 220Kohm resistors (1/2 watt) (Radio Shack)
1 x 100Kohm resistors (1/2 watt) (Radio Shack)
3 x 10K ohm (1/2 watt) (Radio shack)
Heat shrink tubing (slightly larger diameter than diameter of resistors used)

TOOLS:
Multimeter
Various picks such as: 90-degree, straight pick
2 sets of needlenose pliers
Soldering iron
Solder
Work light
Wire cutters (or strippers)
Small flathead screwdriver
Lighter



GETTING STARTED:
1. Park your X, turn off engine and apply parking brake.
2. Set up work light and disconnect car battery negative terminal.




BUILDING YOUR RESISTOR (i.e., “fake knock sensor”):
4. While engine cools, begin process of creating your 560Kohm resistor. I used 2 x (220KOhm), 1x (100Kohm), 3x (10Kohm) resistors for a total of 6 resistors. (You may be able to use less but be sure they add up to 560,000 Ohm (560Kohms). Notice mine added up to 570k ohms on paper, but in reality due to real life tolerances, they really don’t (217+217+97+9+9+9= 549 Kohms actual), hence the extra 10K ohm resistor to get 558 Kohms. I cut the ends of each resistor down to 0.25 inches except for the end leads which I kept default length. These ends will connect to the two engine wires later. I also kept the leads longer between the number 3 and 4 resistor because my chain of resistors would be heatshrinked and bent like a “U” and secured in wire loom tubing with electrical tape to the factory harnesses. See pics.






5. Sheath your resistor assembly in heat shrink tubing, leaving the two ends protruding beyond the heatshrink. It is a good idea to read the resistance with your multimeter again just to be sure you didn’t have any breaks in a solder joint. My assembly read 561 K ohms which includes some resistance from all the connections. Heat the heat shrink across the entire resistor assembly using a lighter or even a candle. Once you have this done, you are ready to work on the wiring harness.



MODIFYING ENGINE HARNESS:
6. For the supercharged Xterras, as you peer inside the engine compartment from the front bumper, left of the engine you will two wiring harnesses side by side, one with a gray connector and the other with a green one (for non-supercharged Xterras refer to plugs in the source links at the top of this how-to). Let’s look at the green connector.


In the lower row of wires in that harness, you will notice a white (kind of a cream white color) and a gray wire next to each other. These are the wires we will be working with.


7. Using a flathead screwdriver to push down on the green connector retaining clip, pull to separate the green male and female connector (you might notice the connector make a pop sound like there was suction- this is because the connector is virtually air tight due to gaskets around the wires where they enter each connector plug). We want the side of the connector closest to the front of vehicle. As you look at it head on, there is a white plastic insert (not shown) where that we need to remove using our 90-degree pick. Be careful here as it does not take much pressure to pry it out and don’t drop the insert into the engine! Once you have surgically removed the plastic insert set it aside for later.

8. Let’s carefully remove the white wire from the green connector. Take your time here. On the engaging side of the connector you will see a very thin green tab that holds the metal box-shaped female pin of the white wire in place in the connector. You will need to use your straight pick and lightly wedge the pick in between the green plastic tab and the female pin. (NOTE: Do not stick your pick into the box-shaped female pin or you will damage it). As you look at the connector end, pry the green tab away from the female pin.


When the green tab has cleared the back of the boxed pin, use your fingers or a set of needlenose pliers to gently pull the wire out of the connector from behind. If you need to, you may lightly push on the boxed female pin from the front simultaneously. The wire should slide out with hardly any resistance.


Once removed, you will notice on this wire there is an orange rubber gasket material where the wire insulation meets the crimped female pin. This gasket insulates each of the wire connections from exterior dirt and moisture. Pretty cool design actually.

9. Now let’s repeat the process in step 8 for the gray wire in the same connector. Using your straight pick, pry the green tab way from the female pin, and pull the gray wire out from behind.


10. Plug in your soldering iron. I have a selectable 15 watt-30 watt iron which I had set to 30 watts. When its ready, get the resistor assembly you made from step 4 and 5 above.

11. Since resistors are non-directional in series, it does not matter which lead goes to which wire. So pick one and hold the soldering iron tip to both the lead and the boxed female pin. I soldered the lead to the outer part of the white wire’s pin for a few reasons: First, this allows me to be able to undo the mod and return the pin back to the connector if I ever needed everything back to stock. Second, I would warn against the temptation to stick the resistor lead into the female end and solder there to avoid damaging the female pin with excess solder which could affect a connection later if everything was returned to stock.


12. Solder the other end of the resistor assembly to the gray wire the same as you did in step 11. Using electrical tape, wrap each of these connections separately to ensure they do not make contact with each other. When finished the resistors have completed a path from the gray wire to the white wire.


13. Sidenote- Whether doing car audio, alarms, home improvement projects or other mods, I am a stickler for neatness. I can’t stand shitty workmanship. Do it right. Often, the difference between a job that came back for problems and one that lasted forever was due to the installer/tech/worker taking care to think about problems before they occur. Things to consider: the engine will get really hot so we want to secure our mod with flex loom tubing to the stock wire harness for several reasons-we don’t want our mod to make contact with a hot engine block and melt something; we don’t want vibration to cause something such as a solder joint to break; we don’t want anything to get caught in moving parts; we don’t want an expensive repair bill for something stupid and easily prevented.

14. Take the flex loom and electrical tape (if you don’t have any loom then just use high quality electrical tape like 3M). Gently fold back the white and gray wires with the resistor assembly attached back and rest it along the wire harness coming from the green connector. Wrap electrical tape in two places around the resistor assembly and wiring harness to secure the assembly on the wire harness.


Bend open your 4-5” section of flex loom tubing and wrap it over both the resistor assembly and the stock wiring harness. This will shield the resistor assembly somewhat from heat, dirt and moisture. Wrap this new loom and stock harness with electrical tape. It should look close to factory in appearance when you are done.




15. There is one last thing to consider. Remember the orange gaskets around each wire? They were there to protect the integrity of the connector from dirt, moisture etc. You can use a dab of silicon sealant and dab it in the two openings in the green connector where the wires used to enter the plug. This will prevent dirt or water from getting into the connector. Alternatively, I cut some spare wire insulation to be used as a plug that was close in outer diameter to the inner diameter of the hole. I removed all copper wire strands from this “plug” with needlenose pliers to prevent any accidental shorting.


I dabbed some silicon adhesive around the edge of this plug then inserted it into one of the holes.

I repeated the process for the second hole. If I ever need to return this wiring to stock, I only need to use a pick to pop each plug out and re-insert the wires.

16. Now that everything has been accounted for, remember that white plastic insert you removed from the green connector in STEP 7? Go get it and put it back on the connector. Now work the male and female ends of the green connector back until they are fully secured.

Here's a pic of the finished product:


And a different angle:


17. Remove all tools from the engine bay and reattach your battery negative terminal.

18. If you have a code scanner that can erase codes, attempt to erase the knock sensor code before starting the Xterra. I checked for codes right after the resistor mod but before I started the ignition and the codes were gone. I believe this was either because the battery was disconnected and/or the ECU detected a "working knock sensor." My scanner has not detected any codes after several trips ( both hard and easy on the gas pedal :) ) and I have not received any new stored knock sensor codes since the mod. I will continue checking engine performance with my scanner and my lead foot for the rest of the week. :D

If anyone has questions or comments, feel free to post... :wink-big:
 

·
Premium Member
Joined
·
264 Posts
Just did this the other day, great results. You will read a lot of "may not be a good idea" threads, but I could not find a single "had problem" thread...

Great write-up. Rep points.
 

·
Premium Member
Joined
·
2,223 Posts
The only thing I'd like to add is that running Premium fuel after this mod would be a great suggestion. Even at around $.40 higher than minimum (average in my area), it's still only around $8.40 per fill up, from absolutely empty, to insure that pinging and knocking aren't going to happen.

Did you check your timing or even do a +2° advance on your engine, if you're running Premium? Just curious, has nothing to do with the mod.

Great write-up! Nice pics, excellent detail work and fantastic explenations. Kudos Jackal!
 

·
Premium Member
Joined
·
698 Posts
Discussion Starter #4
Thanks guys. Cyclemut, no I didn't check the timing or anything and I have always run premium (except for a few months back in '08). I think I'd need to read up on how to mess with the timing but as far as I can tell, the Xterra runs pretty damn solid for 9 years old. Still, I'll consider anything to squeeze more performance out of her. I have my eye on some DT headers, but I think wheels/tires will be coming first later this year.
 

·
Registered
Joined
·
2 Posts
I have a 2002 Natural aspirated engine, I was hoping that I can influence someone with a 2002 Xterra to show in great details a perfect Mod and this is it.
However, just wanted to verify that the knock sensor connections on this harness is located to the right. Also is this the 6 and 7 pins white and grey (or clear looking wires).
I know that it is in the same harness with the injector cabling.
 

·
Premium Member
Joined
·
698 Posts
Discussion Starter #6
In the picture above step 7, you can see the white (cream white color) and the gray wires. As you look at the connector in the pic (i.e. from the front of the vehicle), they are in the green connector, lower row right side, side-by-side to each other. I believe they are pins 6 and 7.

For further clarification the top and bottom rows from left to right:
[gray][yellow/black][orange/black][white/black][black/red]
[empty][white/red][white/blue][gray][white]
 

·
Premium Member
Joined
·
264 Posts
Gostyle - you wont get much benefit from this with an NA motor. The Supercharger goes into failsafe mode when the knock sensor is reporting bad data, so for the S/C guys its a huge performance/mpg drain.

Look into the relocation mod also. I tried both, and the relocation mod did not work for me (knock sensor codes still thrown no matter what I did).
 

·
Registered
Joined
·
121 Posts
my second KS in 60,000 miles just errored last night i cant afford the 1600 cost again .. if i read correctly you then dont have to take the old KS out .. you can basically " trickl " the vehicle into a constant OHM reading from the resistors ??
 

·
Registered
Joined
·
2,004 Posts
Pretty much, if you do some searching you can find a single 560k ohm resistor. I know i did. The only downside is you now have no protection from bad gas so you really need to run premium all the time if you do this on a sc.
 

·
Registered
Joined
·
121 Posts
i run premium FULL TIME anyways .. i just cant afford 1600 bucks at a stealership and dont honestly have the 12 hours of time ( IF I DO IT RIGHT ) to actually replace the other KS

i honestly dont think there is anything wrong with my rig except for a faulty sensor ..

where did you find the single resistor ?

on a scale of 1 - 10 how hard was this job doesnt look that bad if you take your time
 

·
Premium Member
Joined
·
698 Posts
Discussion Starter #11 (Edited)
sanboy it really is an easy mod. Just take your time. I run premium all the time too. I think if you are methodical the mod might take 1.5-2 hours. Others that prep their work early like soldering resistors using the how-to might be able to do it in like 45 minutes or less. I heard the nissan knock sensors are just not durable but the dealbreaker for most is the location which = tons of $.

I'd give the job a 3 on the hard meter. I'd give my "shwing" a 10 after I got it done and my S/C was working properly. LOL.
 

·
Registered
Joined
·
121 Posts
hey jackal
thanx so much ... going to have to try and do this --- just going to go very slow .. LOL .

i do have one question just by looking at the pictures ...

your soldering the resistors to the 2 wires you removed from the green connector ... then i believe you reference " silicone adesive to the plugs "

the wires you have just soldering they are not placed back into the " green connector " correct .. they are folded over and let to " loop to themselves " ???

so when you say " plugs " is where i get a little lost

sorry if it sounds like a stupid question
 

·
Premium Member
Joined
·
698 Posts
Discussion Starter #13
Sanboy since the two wires removed from the connector are folded back and effectively removed from the connector, the silicon and "plugs" take the place of the wire. This is done to maintain the integrity of the connector and not allow dirt or water to get in. It's strictly precautionary especially since alot of X drivers get into water. Hope that clears it up some.
 

·
Registered
Joined
·
121 Posts
it does .. i was " over thinking " it .. LOL

you and I basically have the same vehicle -- I have been going back and fourth on doing the resistor mod compared to the sensor relocation ...

i keep coming back to the resistor way because relocating a sensor to listen to a place it wasnt supposed in my brain seems like a recipe for disaster

have you had any issues with the resistor --- bascially we are tricking the computer to think everyine is ok all the time right
 

·
Registered
Joined
·
121 Posts
it does .. i was " over thinking " it .. LOL

you and I basically have the same vehicle -- I have been going back and fourth on doing the resistor mod compared to the sensor relocation ...

i keep coming back to the resistor way because relocating a sensor to listen to a place it wasnt supposed in my brain seems like a recipe for disaster

have you had any issues with the resistor --- bascially we are tricking the computer to think everyine is ok all the time right
 

·
Premium Member
Joined
·
698 Posts
Discussion Starter #16
Yes we are essentially telling the computer "Move along now, nothing to see here." lol. I haven't had any issues I am aware of.
 

·
Registered
Joined
·
121 Posts
one last question .. how did you decide on multiple resistors ..

i read people are using 460 + 100 one

once again .. great pictures and write up .. thanx so much
 

·
Premium Member
Joined
·
698 Posts
Discussion Starter #18 (Edited)
The only reason I did multiple resistors is because the local radio shack didn't have anything bigger to add up to 560K ohms. If you can find resistors with the exact value then go for it as it will be a tidier installation.
 

·
Registered
Joined
·
2,004 Posts
I got a pack of 560k ohm resistors from frys for $2. They are only 1/4watt but have worked so far. FYI in the 2000 manual it says a value from 500K-620K ohm is acceptable when testing for a bad knock sensor. Pretty sure thats where the 560k is coming from since its the middle.
 

·
Registered
Joined
·
32 Posts
Resistor Mod Fail?

Sorry to steal this this thread. I am a newbe to this forum and have found it a wealth of useful information. That being said I have a 2002 S/C Xterra with the dreaded P0326 knock sensor problem. I did the resistor mod of Jackal's and had great results. My X had long lost power and ran great for a couple of weeks. I have since lost that power and did a scan on it to find a P0327 and P0328 low and high voltage knock sensor codes. I did the mod over thinking that maybe the resistors had failed and came up with the same results, P0327 & P0328. I went back to Radio Shack and to get more resistors and found a 560 ohm resistor. I did the mod over this time with just the single 560 ohm resistor and had the same two codes come up. I have always ran premium fuel before and after the mod. Does anybody have an idea what could be going on here? I am a loss because I thought the resistors were bypassing the knock sensor and tricking the computer into thinking everything was functioning fine. I dont know what to do now to correct this and get that great power back. Resistor relocation? or do the laborous job of replacing the knock sensor only to have it go bad in a short amount of time. Any help or suggestions is greatly appreciated.
 
1 - 20 of 110 Posts
Top