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Discussion Starter · #1 ·
Hello,
I tried to do a search on this, but I had no luck finding anything on this particular swap. I took the drivetrain out of a 96 zj and put it in a 95 yj. The motor and trans is physically in place, and now Im trying to sort out the best way sort out the wiring harness issue. I was hoping to use the dash harness from the yj and retain the original gauges, and use the engine bay harness, engine harness, pcm and power distribution box from the zj, and just eliminate the air bag, abs, and air conditioning wiring. I thought i was going to be able to make this work, but when it came to gauges, the way the zj gauges are powered is way different from the way the yj gauges work. The zj gauge cluster is " an electro mechanical unit that uses integrated circuitry and information carried on the chrysler collision detection (CCD) data bus network for control of all gauges and most indicator lamps". Thats how the service manual describes it. then there is the issue of the body control module, which im still not sure how that is tied in to things. The yj gauges take an actual vehicle speed sensor signal, and a tachometer signal input, so I dont know if its possible to use the original yj gauges with the zj harnesses, or if its even possible to modify the harnesses.
I figure surely theres got to be someone who has done this swap before and can enlighten me on the best way forward. I dont know if its possible to just run the engine, trans and pcm from the zj, and use the original yj harnesses for everything else, or what to do exactly. Any help from those smarter than me would be appreciated.
 

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Do you have the YJ PCM/ ECM?
 

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I found the easiest way to do this is to use the wiring and computer for a 94-95 YJ. If your jeep came with the 2.5 then some have taken and added a couple injector wires and computer to make it work. But I like simple and did the whole swap of wires. Ebay is a good source for that harness. Lot of times it comes with the computer too.
 

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Discussion Starter · #4 ·
I do have the harness and pcm from the original 2.5 w/ manual trans that was in it. I assumed the issue with that was that there is no transmission controller, so That's why I assumed I'd have to use the pcm and harness from the zj. Part of me feels like I'm making this way too complex, but not sure how to get around the transmission control issue.
 

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I over looked the part of the trans being a auto. That makes this a little more of a pain and you got to use a controller for the trans,
 

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Discussion Starter · #6 ·
Today I considered putting an aw4 behind it instead of the 42re, because that has a semi stand alone tcu from what I understand, but evidently there is some additional wiring to do there, plus I already installed the SYE and had a driveshaft built for the np242, so I feel like I've invested too much to change transmissions now. I think I've got a workaround to be able to make the zj gauges work in the yj, basically mount the cluster circuit board under the dash and wire the zj gauges separately off of that mounted in the yj locations. More work, but doable. I'd love to eliminate the body control module and alot more of this dash harness wiring, but I think it's all got to stay for it to work. I'm preparing myself for this to turn out to be a giant disaster.
 

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I just did a bunch of searching because I thought this had popped up before, and it had.

Nobody has the answer. You'll have to figure out the wiring yourself, or use a different transmission. Or use a Novak shifter and just treat it like a clutchless manual.
 

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I just did a bunch of searching because I thought this had popped up before, and it had.

Nobody has the answer. You'll have to figure out the wiring yourself, or use a different transmission. Or use a Novak shifter and just treat it like a clutchless manual.
I sorta opt for that option.

See if you can find out the minimum data the trans needs to shift. If it's only RPM and throttle position (?) you might be able to run everything on the YJ harness and 4.0 ECM and steal those data points to feed the GC ecm to the trans.
 

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Discussion Starter · #11 ·
Sorry for not responding sooner. I haven't been checking back until I had more news to share. So as of now, the motor starts and runs. I spent a day trying to figure out why it would crank, but not run. I double checked to make sure I had all my engine compartment grounds attached, and in the end I finally found a wire that I had cut for some reason that supplied power to the coil,and after I connected that, it started right off. I've only ran it for a out 15 seconds since I didn't have any coolant in the radiator, but I'm reasonably sure it's running on all cylinders . My next step was gauges. I have no gauges or warning lights or odometer at the cluster. I've got the left turn signal indicator and a couple of back lights. Nothing else. I'm using the factory ZJ cluster with the CCD Bus system. I've spent a couple days now chasing down grounds in the cabin and making sure they are connected. I've got power and grounds to the cluster. All related fuses good. I tested the CCD Bus + and - wires, and I have 2.38 and 2.39 volts at those, which is within tolerance. I hooked up a scanner to it it seems to communicate properly. I have two codes, one for the battery temp sensor, one for the evap system, which I haven't hooked up yet. Im at the end of my knowledge as to why I have no cluster. I just asked last night over at the zj forum to see if anyone had any ideas, so we will see if anyone does. I'm leaning towards it just being a bad cluster at this point, but I have a hard time believing that, because I'm fairly sure it worked before I took the drivetrain out of the zj. I just can't think of anything else it could be. So, that's where I am today. My options are to get another cluster from the junkyard and try it, Or just take it down the road and see if it runs and shifts properly. If it does, I could just throw some autometer gauges in it, wire them direct, and abandon the factory gauges. I wouldn't have a check engine light, but considering it does communicate with a scanner through the data connector, I could still check codes. I'm not sure if the transmission requires CCD Bus info to shift properly or not. I guess the CCD Bus signals tested out ok at the data connector,so maybe all that is functioning properly, and it's just a cluster issue. I'll keep plugging away at it and keep updating as it goes along, for better or worse.
 

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using the factory ZJ cluster with the CCD Bus system
Isn’t there a separate ecu for the cluster?
Or am I confused?

I’m just wondering if you couldn’t test the pins and at least see if the signals are being sent. Then you’d know if it’s in the communication cables or at the cluster?
I dunno. Just trying to help
 

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Discussion Starter · #13 ·
Update:
I'm abandoning the zj gauges and most of the zj harness. I'm going to use the original YJ harness for everything except the wiring to the pcm required to make it run and shift. This may require me to wire the yj gauges direct to each sensor rather than through the pcm. Tach may be an issue, but I think everything else will work that way.
 

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going to use the original YJ harness for everything except the wiring to the pcm required to make it run and shift. This may require me to wire the yj gauges direct to each sensor rather than through the pcm. Tach may be an issue, but I think everything else will work that way.
Your zj pcm will want to know some things. Temperature, cps etc.
 
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