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ECM Question

1816 Views 5 Replies 2 Participants Last post by  jeepnfool
Ok, I have a 97 TJ that had a 4.0 in it. However, the guy I got it from put a 4.0 in it from an 96 XJ but didn't have the TJ harness or computer, so he put the XJ computer in it. I have the project now and have the TJ harness. Question is, will the XJ computer work, or do I need to buy one for a 97 TJ?
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There's tons of knowledge here in this forum, but just like Google, you have ask the right question and give us a little more to work with.

First off, if the Jeep originally had the 4.0, why was the PCM changed?

Second, why change wiring?

If I'm reading the original post correctly, the Jeep came from the factory with the 4.0. If that's right, a simple long block changeout would have been an easy deal.

So from my standpoint, I'm trying to figure out where the whole thing went crazy and start from there.

More info?
 

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Discussion Starter · #4 ·
Dave, I don't know what other info you need.

1. I bought the jeep 3rd hand.

2. The guy I bought it from bought it with no drivetrain, wiring harness, or ecm.

3. Since it originally had the 4.0 in it, he took the entire drivetrain (motor, tranny, tcase) and ecm out of a 96 XJ and put it in it.

4. He did not take the engine harness out of the XJ though.

5. I now have an engine harness from an original 97 4.0 TJ that I am going to use.

6. Question I have is will the XJ ecm work or will I need to get a TJ ecm?

I have searched this site and many others, along with google and can not find the answer.
 

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That's the info we needed! You will need the engine harness for a TJ, no question. The PCM needs to be from the same setup, I'm pretty certain the 97 or 98 will work. If you need a wiring diagram let me know and I'll figure out a way to get it to you.

Unless I'm way off, the XJ has 4 connections on the PCM the TJ only has 3, as I remember the XJ.
 
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