When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm new here, just picked up a 85 pickup SR5. The PO pretty much butchered the wiring, I'm sorting through it. I've come across a single wire from the transfer case, I believe it goes to the harness under the intake manifold where I have a cut single wire. What is this transfer case wire for? Do these trucks have a indicator light on the dash that illuminates when you put it in 4WD?
I’m taking a guess here and I’m sure someone will chime in if I’m wrong but in my 91 the wire that comes out of the t case triggers my reverse lights, I had to tap into it for my reverse camera. BUT the 4wd light I believe is kinda the same off the t case. So now I’m confusing myself as I can’t remember if I have two wires or just the one. So really I’m no help I guess I do have a 4wd indicator on my dash but it’s a 91 so not 100% on the 85.
Last edited by Discombobulated; Jul 29, 2025 at 01:28 PM.
Well now that I’m thinking about it the wire off my transmission is for the reverse and the one off my t case is for my 4wd indicator
On my 85 there is 2 wire from transmission that connects under the intake, this is the reverse lights. I was able to confirm my truck has a 4WD indicator light on the dash, and the light bulb is good. But still can't figure out where this single wire from the transfer case connects to. Hoping someone will chime in with a connection point for the single t case wire
yes .. there is a bulb/indicator as you found ... here is a schematic . red w/Yellow stripe wire .
If you have a power probe , just put 12V to the wire you found and if the light on the dash lights up .. thats the wire !
yes .. there is a bulb/indicator as you found ... here is a schematic . red w/Yellow stripe wire .
If you have a power probe , just put 12V to the wire you found and if the light on the dash lights up .. thats the wire !
Thanks Slacker,
I applied 12v to the cut wire I found under the intake. My 4WD light did not come on. So that's not the wire I'm looking for. I'm hoping someone knows or can peak under their truck and tell me where this single wire from the transfer case connects.
I'm new here, just picked up a 85 pickup SR5. The PO pretty much butchered the wiring, I'm sorting through it. I've come across a single wire from the transfer case, I believe it goes to the harness under the intake manifold where I have a cut single wire. What is this transfer case wire for? Do these trucks have a indicator light on the dash that illuminates when you put it in 4WD?
Yes, indicator on the dash for 4WD. Also, it runs into the engine computer and I think there are a few small changes that makes in ECU function while in 4WD.
Solved! Looking at the wiring diagram did nothing, all it told me was the wire leaving the transfer case was red w yellow. I ended up finding a pin out diagram of the ECU. That led me to the same red w yellow wire. I followed the ECU red w yellow wire to a small connector near the ECU, at that connector the wire changed to light green (mint green) and went to engine bay. I found the light green wire in the harness under the intake manifold. It was cut with no connectors, and buried in the harness, likey a sin from a previous owner. I connected the light green wire to the red w yellow from the transfer case and my 4x4 dash light works.
Jul 29, 2025 | 07:36 AM
I do have a 4wd indicator on my dash but it’s a 91 so not 100% on the 85.
