I bet none of you guys want to touch this topic considering all of you have at some point been traumatized by broken wires and bad grounds that involved some degree cutting, splicing, crimping and cussing.
I just bought a 1995 GMC Jimmy and to my horror found four unplugged wiring harnesses on the left side of the engine compartment. I isolated one of them as belonging to ABS control module, but the other three I haven't a clue. The Service engine soon light does come and the car runs really rough at idle (like an emissions control module is unplugged or mismatched).
Any insight you gentleman could offer would be helpful.

 

The one harness you identified as ABS control mod... It has 2 plug on it?
What engine does your new 95 Jimmy have?
Does it have gauges or lights?
Does it have Cruise Control?
5spd or automatic?

 

Glenn,
Thank you for your response. Sorry for the delay, but I've been really busy chasing other problems on this truck like this miss. Here are the answers to your questions:
The car is 1995 GMC Jimmy with a 4.3 Liter Vortec V6 in it.
The harness that I mentioned as belonging to the ABS Control Module reaches only that far and has the two prong connector on it to match. However it is broken and needs to be replaced. The ABS light is not on, which makes me curious as to whether this vehicle was originally equipped with ABS or not as the Master Cylinder has recently been replaced and is leaking. Possibly the wrong one.
It has gauges and lights. Gauges for fuel, rpm and speed, temperature and a Service Engine Soon Light which only intermittently comes on after replacing the Intake Air Temperature Sensor still shooting back the same code 23 calling for a low temperature reading. I already cut the harness open to look for a broken wire, but could not find one although the wires are hard and brittle creating the other issue of the current not flowing freely through them. Only one way to check this I'm working on it, but I do need to know the numbers that I'm looking for as I'm sure the resistance is different at different temperatures.
I did not readily check for cruise. It's an automatic.
What I really need is a picture of the left side of the engine compartment on this vehicle as all four harnesses are in close proximity to each other.
I was able to obtain a wiring diagram, however I can't be certain that I'm looking at the right one as the VIN sticker is faded beyond the point that it is legible and the car has no catalyst which is poses one final problem that this may be two different vehicles.
Thanks in advance for any help you can provide.
Emmanouil

 

I don't know if you have tried this, but it might be worth a try.
Go to google and do a search "1995 4.3 liter Vortec V6 engine wiring" then click IMAGE I got quite a few results hope this helps

https://www.google.ca/search?q=1995+...Q&ved=0CBwQsAQ