2013 Dodge Ram 2500 4WD wiring harness repair
Channel: Kevin Martin
Date: 2020-06-13

Fair warning, this is a bit of a Blair Witch video with plenty of shaky, out-of-focus, or strangely framed bits.


For most of the past year I've had trouble with the 4WD shifting on my Ram 2500. During the winter I tried replacing both the shifter motor assembly and the Drive Train Control Module (DTCM) which controls it, to no avail. I finally determined it was a problem with the wiring harness, and I ran a temporary wire alongside the harness just to get things working.


Now that the weather is nicer it was time to inspect the harness damage in case other wires had problems too, and indeed another wire had broken.


In this video, I free up the harness from some of its attachment points, strip off the casing, repair two broken wires and tape up another that just had insulation damage, and put it all back together again.


I had suspected rodent damage but when I saw how smooth the worn area of the harness was I concluded that it had just chafed against something, though I never ascertained what. The worn area is so smooth and round that it looks like it was rubbing against an axle. Now that everything is reinstalled I really don't understand where it could have been rubbing.


I spliced in new sections for the two broken wires, using sealing heat-shrink tubing on the splices. I taped the worn insulation on the third wire (it is a +5 volt supply to the shifter position sensor). Then I taped all the wires together, and put two layers of plastic wire mold over the area. I added more tape to hold that in place, then zip ties at either end because the tape by itself is not to be trusted.


There is a retainer, shown by itself around 8:15, which is supposed to hold the harness clear of the transfer case. The retainer was broken when the harness was removed (this happened in the winter repair) so I had to drill a hole in it, and zip-tie it to the hole it should have inserted into. The hole can be seen around 3:00 as a small white dot in the upper-right corner of the boss on top of the transfer case, to the right of the harness.


Altogether, the harness is retained by:
- the connector at the shifter motor
- a retainer near the shifter motor that inserts into a hole in the transfer case
- the retainer I had to repair, where the harness passes over the  output section of the transfer case
- a clip that holds the harness to the transfer case vent hose.
- beyond that, other side branches of the harness attach to various places.