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Unread 05-11-2009, 04:04 PM   #1
Giviner
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TJ Gen3 engine swap - wiring questions

I am in the process of pulling the stock 4.0L. I am looking at my wiring harness and i'm a bit confused.

I am planning on removing the jeep computer and running only the Chev PCM (with aftermarket gauges). I still however, want to keep all functions such as headlights, turn signals, horn, brake lights, A/C etc. Looking at the jeep harness, it is damn confusing trying to figure out what I need and what I don't. I am brutal with wiring which is probably why i'm having such a difficult time with this.

From what I can see, the harness comes through the firewall just below the clutch master cylinder, and splits. One leg of it goes to the headlight/turn signal harness, the other follows the top of the firewall over to the passenger side where it splits again, on leg going to C3 on the jeep computer, the other leg going to the fuse panel.

Anyone care to take a stab at how to proceed from here? Do I need to start tearing into the harness or what? I know I don't need the computer to run things like what I mentioned above (lights/AC/etc). Is it worthwhile to just find the wires I need coming through the firewall and cut everything else, then run my own wires to the fuse panel?

I have all the wiring diagrams but as I said.......i have no clue when it comes to this kind of crap. Any help is much appreciated.

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Unread 05-11-2009, 04:12 PM   #2
RnEmOvr
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you can do this a few ways, since my guess is you are no longer running the Jeep gauge cluster you can make your own harness (cheapest) that wil go from the brakes and lights and radio and what ever else is needed, or you can talk to painless wiring (easiest) and see if they can make you a harness for what you need, they may even carry something like that, or another cheap route is leave the jeep harness in there and just disconnect/cut off whats not needed
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Unread 05-11-2009, 05:26 PM   #3
lumpster
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i have never had any luck getting what i need out of a harness and "cutting the rest".


buy a factory service manual for your jeep, dig into the harness, and find out what ever wire does.

I did this exact swap, aftermarket autometers and a 5.3. got rid of the jeep computer and just ran chevy one. worked great. give yourself a week or 2 to get familiar with all the wires, dont rush it.
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Unread 05-12-2009, 12:06 PM   #4
mattamd_xp
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The only benefit you will get by splitting apart the stock harness on the Jeep is a cleaner looking install. You can just unplug everything that you are removing (such as the computer and any other electrical parts pertaining to the old motor) and leave the plugs/wires in the Jeep. I personally would remove the entire harness from the Jeep and lay it out somewhere I could compare it to the factory service manual and eliminate all unnecessary wires & plugs from it for the cleanest install possible. Just take the looms off the harness once it's out and trace the wires you don't need, remove them and rewrap the harness with just the necessary wires.
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Unread 05-12-2009, 12:18 PM   #5
Zew
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I had a plain ol haynes manual for both the 98 TJ i have and the 01 Dodge ram i pulled my 5.2 out of. I was able by looking at the electrical schematics on the TJ manual to figure out what each wire did. Take your time. You'll find the ac, fuel pump and whatever else you need.

I'm no wiring genius. If i could sort it all out... So can you. You're going with a custom engine harness, it'll be easier. I mated two stock harness'.

You can do it!
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Unread 05-12-2009, 02:37 PM   #6
Giviner
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Thanks for the input guys. I really do want to have the cleanest install possible especially since if I do end up having to troubleshoot wiring in the future I don't have 400 wires that do nothing under my hood.
I never thought about pulling the entire harness out. How difficult is it? Do I need to tear apart my dash or what?
I spent some time last night looking over the FSM and all the associated wiring diagrams and I suppose my initial confusion is in actually reading and understanding the wiring diagrams themselves. I know that certain tags represent terminals on a connector, others represent circuits, etc..........and there are so many different ones. I don't have a feel for how everything ties together yet so it is fairly overwhelming.
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Unread 05-13-2009, 11:45 AM   #7
Zew
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To pull out the harness you have to unplug everything from the engine, unbolt the fusebox under the hood, and disconnect everthing from the fuel pump forward towards the ECU. Its not that hard.
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Unread 05-14-2009, 12:27 PM   #8
Giviner
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Quote:
Originally Posted by Zew View Post
To pull out the harness you have to unplug everything from the engine, unbolt the fusebox under the hood, and disconnect everthing from the fuel pump forward towards the ECU. Its not that hard.
I've got everything under the hood apart. From what I can tell on the inside I will need to pull the dash apart to get at all the connections in there.

I have been doing a lot of research and planning over the past few days and when I think about it, it shouldn't be that difficult.......i don't need any wires associated with engine/powertrain management, so if I remove all of them, all that remains should be what I need.

Also gives me the chance to remove a few features that I don't like, such as the seatbelt buzzer, door open buzzer, and all of the stock stereo wiring.

Also, for what it's worth, i have been contemplating giving the engine harness a shot on my own. I have been using this site:

http://www.lt1swap.com/

and there is tons of detailed info there on how to do it yourself....i've only got about 400 questions so far, but i am beginning to understand it a bit.
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