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I have a 93 YJ that currently has a 2.5 and ax5. I am swapping in a 4.0 and a aw4 auto transmission from a cherokee. Should I use a computer and engine harness from a wrangler or do I need to use the one from the cherokee. I have access to both. I know I need the separate computer for the transmission but I'm not sure which one to use for the engine.

Thanks,
Jason
 

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You are going to want to use the entire underhood harness from the cherokee. Also, what year cherokee? The OBD2 XJs use a higher pressure returnless fuel system that you may need to adapt. If that is the case, you may try to source the engine harness and pcm from a 4.0 yj, and then add the tranny wiring as if it were an aw4 swap after.

I am just finishin up swapping an aw4 into my 4.0yj, and chose to retain all the xj underhood wiring for the swap. It was a 96 and did require the fuel system be updated as well.

Basically, all I did was cut the xj bulk connector off and splice on the yj one. It is obviously alot more complicated then that, but not as hard as you may think.
If you choose to use the xj wiring, I strongly recommend you buy a subscription to alldatadiy.com for both vehicles. It will be the best $45 you spend, as simply following wires will not give you the whole story on what is goin on.
 

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I am gaining knowledge to do a similar swap (96 XJ 4.0 and AX15 in 95 YJ 2.5). I do not have the harness from the donor vehicle. I was told I should use the 2.5 harness and splice in four wires to run the extra two fuel injectors. Use a 95 YJ 4.0 computer. I was told I needed to use a 1998 4.0 distributer pick up and a 1995 MAP sensor. Outside of fuel line is this about right?
 

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I see no reason at all to need to run a 98 dist. pick up to run a 4.0 with a 95 computer. Why not use the 95 pick up the 95 computer will be looking for?

That said, without part numbers in front of me, I am not sure if they are the same or not from any year the 4.0 HO was in production. I would check the PN's to see if they 96 matches the 95. If so, run what came with the engine.

As for the adding wires, it sounds correct, but I cannot say for sure that the 2.5 and 4.0 pcm pin outs are the same. My bet is that they are, but I am unsure.
 

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Yea it sounds like voodoo. Like I said I am gaining knowledge. Unfortunately I don't possess that knowledge yet. Info came from a rep at HESCO when I asked if they could put together a harness for me. He said "no" to the harness then added his expertise on what I was doing. I figure take everything I can from a 95 4.0 YJ and use the 96 XJ engine. Same block and head right? Also I'm staying manual trans so I dont have to worry about that.

Sorry didn't mean to hijack the thread.
 

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Yes the head and block are the same. I would verify the part numbers on the sensors for the 96 engine to see which ones you can use with the 95 pcm. I know off had that the 9 will have an Intake Air Temp sensor that the 95 will not need. The 96 uses an integrated MAP while I believe the 95 uses a remote mounted MAP(on the firewall). I am unsure if they will interchange.

You are also going to need the fuel rail off the 95, although I would think any 91-95 4.0 fuel rail would work.
 

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Wiring harness is the same.Pin 38 is tne number 5 injector and 58 is number 6 injector.
Just did the swap with a 99 motor in a 94 yj.You will have to extend a few wires but not many
 
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