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SOLVED - Wire 4wd indicator light after 2wd to 4wd conversion

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J
Got a project 2001 xj and just finished the conversion from 2wd to 4wd (automatic with np 242). Everything is working great.

My question is, has anyone had any success wiring up the 4wd indicator light after doing this conversion?

I know the 2wd and 4wd transmission harnesses are different, so I'm assuming I'll have to wire it in by finding the 4wd indicator wires somewhere else in the vehicle.

Or maybe there's no way... just want to make the conversion as complete as possible.
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CJ7-Tim
It has been done. I have read some threads in the past about swapping from NP231 to NP-242 and having to bridge a wiring gap from the firewall area to get the Full-Time lamp to indicate.

Are you sure the 2wd wire harness does not have a transfer case wire plug ? You could keep an eye on the local junkyard for a NP-242 97-01 Cherokee and scavenge the section of wire harness you need.

Section 8W - 40 - 7 of your Factory Service Manual has a diagram of the 4wd t-case to dashboard wiring.
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CJ7-Tim said:
It has been done. I have read some threads in the past about swapping from NP231 to NP-242 and having to bridge a wiring gap from the firewall area to get the Full-Time lamp to indicate.

Are you sure the 2wd wire harness does not have a transfer case wire plug ? You could keep an eye on the local junkyard for a NP-242 97-01 Cheerer and scavenge the section of wire harness you need.

Section 8W - 40 - 7 of your Factory Service Manual has a diagram of the 4wd t-case to dashboard wiring.
Click to expand...
I actually just got it working. Here's what I did...Hope it helps someone else.

I had the original harness at the T-Case that plugs into the mode indicator switch. To tie it into the system, the C107 connector is the best place to tie in the wiring harness from the T-Case for the mode indicator lights. The C107 connector is a black 14-pin (only 12 wires though) at the back of the engine bay on the passenger side just below the transmission connectors.

For the NP242 there are 3 wires on the t-case mode connector. I spliced into these with some 18 gauge wire and made 3 runs up over the trans to the connector. I peeled back the loom to expose the 12 wires on the C107 connector. The black/white wire from the T-case mode indicator harness goes to the black/white wire in position 12 (G106). The black/red wire goes to the black/red in position 8 (G107). The black wire (ground) from the indicator harness just needs to be grounded to the frame somewhere that makes sense.

For the NP231 there are only 2 wires black/red and all black. You do the same thing as above, just omit the black/white wire that splices to position 12.
Rectangle Font Parallel Number Pattern
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O
joshmoch said:
I actually just got it working. Here's what I did...Hope it helps someone else.

I had the original harness at the T-Case that plugs into the mode indicator switch. To tie it into the system, the C107 connector is the best place to tie in the wiring harness from the T-Case for the mode indicator lights. The C107 connector is a black 14-pin (only 12 wires though) at the back of the engine bay on the passenger side just below the transmission connectors.

For the NP242 there are 3 wires on the t-case mode connector. I spliced into these with some 18 gauge wire and made 3 runs up over the trans to the connector. I peeled back the loom to expose the 12 wires on the C107 connector. The black/white wire from the T-case mode indicator harness goes to the black/white wire in position 12 (G106). The black/red wire goes to the black/red in position 8 (G107). The black wire (ground) from the indicator harness just needs to be grounded to the frame somewhere that makes sense.

For the NP231 there are only 2 wires black/red and all black. You do the same thing as above, just omit the black/white wire that splices to position 12.
View attachment 4170539
Click to expand...
Man, you are the king!

I was breaking my head trying to figure out how to go about this and reading diagrams.
My thought was to run a cable all the way to the dash to that black/red wire but this is much easier and elegant solution.

I have 2 questions for you:
1. Where did you ground exactly?
2. What method did you use to splice in factory wires on the c107 connector?

Thanks!

Edit: after rereading your post I'm not actually sure you spliced into the wires on the c107 connector.

Would really appreciate if you could elaborate more.

Thanks again!
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oprtb said:
Man, you are the king!

I was breaking my head trying to figure out how to go about this and reading diagrams.
My thought was to run a cable all the way to the dash to that black/red wire but this is much easier and elegant solution.

I have 2 questions for you:
1. Where did you ground exactly?
2. What method did you use to splice in factory wires on the c107 connector?

Thanks!

Edit: after rereading your post I'm not actually sure you spliced into the wires on the c107 connector.

Would really appreciate if you could elaborate more.

Thanks again!
Click to expand...
For the ground I just found the nearest bolt/screw going into the chassis in the engine bay. Just make sure to rub off the paint so you make good connection.

For the splice, I used these.....
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joshmoch said:
For the ground I just found the nearest bolt/screw going into the chassis in the engine bay. Just make sure to rub off the paint so you make good connection.

For the splice, I used these.....
View attachment 4187104
Click to expand...
Excellent!
So I assumed right, you did splice into the factory wires.

I am debating if I should cut the wire and make some connector but I'm probably overthinking it.

What did you do with the 3 prong speed sensor connector, from what I heard that one needs to be extended?

Again, I hate cutting into factory wires so I bought pigtails and made extension basically.
Hopefully it works fine.
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oprtb said:
Excellent!
So I assumed right, you did splice into the factory wires.

I am debating if I should cut the wire and make some connector but I'm probably overthinking it.

What did you do with the 3 prong speed sensor connector, from what I heard that one needs to be extended?

Again, I hate cutting into factory wires so I bought pigtails and made extension basically.
Hopefully it works fine.
View attachment 4187111
Click to expand...
The speedo connector was tight, but I was able to stretch and make it fit. Don't cut the factory harness, just splice into it and it will work perfectly.
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joshmoch said:
The speedo connector was tight, but I was able to stretch and make it fit. Don't cut the factory harness, just splice into it and it will work perfectly.
Click to expand...
I just read bunch of bad things about those vampire connectors hence I'm hesitant on using them.
But anyways, I'm very grateful I found your post and appreciate your help.

How is jeep performing as 4wd?
Any other tips & tricks you could share before I start doing it?

I'm almost done with the axles so next step is transmission and all that.
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oprtb said:
I just read bunch of bad things about those vampire connectors hence I'm hesitant on using them.
But anyways, I'm very grateful I found your post and appreciate your help.

How is jeep performing as 4wd?
Any other tips & tricks you could share before I start doing it?

I'm almost done with the axles so next step is transmission and all that.
Click to expand...
Other than a slight loss of MPGs, everything is running great....so far :)

Here's my list of things did that made things easier:

For the install
  • The best thing I did was put my SYE on while the 4wd tranny was on the ground (before install).
  • Upgrade the T-Case shift linkage before install, then adjust once everything is set.
  • I used a local driveline shop to build a custom rear driveshaft to fit.
  • Be prepared to buy new transmission cooler line connectors or have them on hand. Mine fell apart while taking out the 2WD tranny.
For the interior
  • I ordered a shifter bezel and lighting harness from ebay. The lighting harness for the 2wd XJ, in the center console only has 1 light, for the transmission shifter. But you can follow it back under the arm rest compartment and it has a harness plug under there. You can simply swap for the 4wd 2 light harness and then have both bezels (tranny and t-case) illuminated when you turn your headlights on.
I also ordered 4x4 badges from ebay and put them in the stock location. There's no way, by looking at my XJ someone would know it wasn't always 4wd!

This was all on my '01 XJ. Your year, if different, may not be exactly the same.
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K
I have to agree that those "splice connectors" are absolute garbage. As a professional electrician, I absolutely hate them. Hell, I would hesitate to use them for temporary use!
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KF4SQB said:
I have to agree that those "splice connectors" are absolute garbage. As a professional electrician, I absolutely hate them. Hell, I would hesitate to use them for temporary use!
Click to expand...
Well, they were about my only option with how tight that connector is between the back of the engine and the firewall. Getting a proper splice on it was next to impossible. The good thing is....if those fail, I only lose my 4WD light. (y)
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joshmoch said:
Well, they were about my only option with how tight that connector is between the back of the engine and the firewall. Getting a proper splice on it was next to impossible. The good thing is....if those fail, I only lose my 4WD light. (y)
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At least until, depending on HOW it fails, it shorts to ground and blows a fuse. What all have you lost now? Ask me how I know about the possibility of something like this happening! 😉

However, I understand what you mean about clearance. They didn't exactly make these things the easiest to work on for some things, did they?
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joshmoch said:
Other than a slight loss of MPGs, everything is running great....so far :)

Here's my list of things did that made things easier:

For the install
  • The best thing I did was put my SYE on while the 4wd tranny was on the ground (before install).
  • Upgrade the T-Case shift linkage before install, then adjust once everything is set.
  • I used a local driveline shop to build a custom rear driveshaft to fit.
  • Be prepared to buy new transmission cooler line connectors or have them on hand. Mine fell apart while taking out the 2WD tranny.
For the interior
  • I ordered a shifter bezel and lighting harness from ebay. The lighting harness for the 2wd XJ, in the center console only has 1 light, for the transmission shifter. But you can follow it back under the arm rest compartment and it has a harness plug under there. You can simply swap for the 4wd 2 light harness and then have both bezels (tranny and t-case) illuminated when you turn your headlights on.
I also ordered 4x4 badges from ebay and put them in the stock location. There's no way, by looking at my XJ someone would know it wasn't always 4wd!

This was all on my '01 XJ. Your year, if different, may not be exactly the same.
Click to expand...

Thank you for that!
I have all parts so hopefully it goes well. This weekend is the d-day.

So I have been looking at the wiring diagrams and tracing what I have on my Jeep (2wd) and the donor (4wd).

Here is the main diagram:
Slope Rectangle Font Parallel Pattern


We can see here that C112 (the one on top of the TC which is in charge of the 4wd light) goes directly to the C107 connector (the one you spliced in) and then from there to the C2 which is a a dash connector.

I traced wires on the c107 and they both have black/red wire.. 2wd and 4wd.
That makes me think that the transmission wiring harness is maybe missing that wire somewhere.

Now I was not able to look at the transmission wiring more obviously as I didn't pull it yet but I'm aware that c107 is a pigtail that plugs into something else on the trans harness.
Maybe some wire is missing there?


I would be curious to hear your thoughts.
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