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mike1305

1992 Wiring Issue - 1994 Manual has differences I need to diagnose!

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Hey folks,

 

Big help last time with my dash regulator in the previous post, it's definitely all working as it should and has been replaced already. So that's not what's blowing the meter fuse. I found it after some flashlight time under the hood. It's the classic "wire melted on the exhaust manifold". Wow does that look like a pain in the ass to fix. It's totally fried.

 

The issue now is that the closest service manual I can find for my 1992 is for a 1994 model, and there is one difference I'm spotting that's throwing me for a loop.

 

Images: https://imgur.com/7l0yR2r

 

There are two wiring looms that travel from connectors on the right wheel well, over the manifold, and down thru the trans tunnel to a handful of sensors all over the transmission. One of them has been deep fried on the griddle that is the exhaust manifold, and has to be the reason my meter fuse is going kaput (see photos 1 and 2 in the attachment). Given the truck runs fine without the fuse working, aside from no dash gauges (who knows what electrical @!*% the P/O did to make that happen), I'm just going to disconnect it and see how she does. BUT that doesn't really solve the problem. I'd like to get things in working order again...

 

I popped into the 94 harness layout and determined these were connectors 1E and 5E (see photo 3). Okay cool. Can't really tell which goes to what as they seem to magically merge in the photo. I go to the wiring diagram (photo 4) and realize why they magically "merge"... because in a 1994, there should be one or the other depending on if you're rowing your own or slushing around. So why do I have two?

 

Even after the meter fuse blows, I still have a working tach (edit: working SPEEDO. Tach goes with the rest of the dash). I see there's a vehicle speed sensor on that circuit, as well as a backup lamp switch, transfer switch, neutral position switch. 4WD also works (not 100% sure if that is what "transfer switch" refers to...). Perhaps the second, non-damaged wire loom is for the speed sensor and 1992 models just had them separated out? I can't find a good photo of a 1994 for reference. the 1991 in photo 5 (from this amazing auction) shows two sets of looms... so... yeah I'm just confused.

 

Any help understanding this is appreciated!

Edited by mike1305

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A lot of electrical differences between 92 and 94. 1992 had a mechanical speedometer and had a speed sensor in the speedometer head for the cruise control. 1994 used a speed sensor in the transfer case or transmission for the 2 wheel drive that ran the speedometer and shared the info with the cruise control and ECU. The wiring is different and not interchangeable. 

The transfer case wiring is for the 4wd light. The 4wd is strictly mechanical in our old trucks. 

 

The automatic transmission is electronically controlled so you do have a wire harness going down there as well as the O2 sensor. The O2 sensor wiring is its own harness that runs along the transmission harness. 

Edited by Mr_Reverse

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Thank you :) is there a diagram for a 1992 anywhere? Or do I just need to play guess and check. The burnt loom has a ton of wires but the good one just has black red white. Wondering what that one controls. Maybe the 02 sensor and the rest is backup light, neutral switch, and ???

Edited by mike1305

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It’s also a manual FWIW. 

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I don't have a '92 manual (or one for my '93, unfortunately), but cardiagn has a '90.
 

Black/red/white should be the oxygen sensor, yes.

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The red, black, white wire harness is the O2 sensor. The other one should have wires for reverse, neutral, 4wd, and 5th gear(I think) switches. 

My computer died yesterday that had the FSM for my 93 in it. Monday, I can look it up at work on Alldata, but it shouldn't be too hard to follow the harness and see what all it goes to. Mine is automatic transmission and I have tinkered and altered so much of it that it is a poor guide. It doesn't even have an ignition lock anymore. 

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