Strokermjcomanche Posted July 7, 2015 Share Posted July 7, 2015 I have an 88 mj with a 4.0, 4x4 ,5spd ,air and the body harness is shot . It's the harness that screws in the fuse block at the firewall and goes to the engine compartment , houses the relays , goes to the front light harness etc I have a 2.5 body harness from a 88 with Air , 5spd , will this work ? Thanks in advance Link to comment Share on other sites More sharing options...
dasbulliwagen Posted July 7, 2015 Share Posted July 7, 2015 I don't think so. Pcm wiring is all different. Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 7, 2015 Author Share Posted July 7, 2015 I don't think so. Pcm wiring is all different. Thank you dasbulliwagen , looks like I'm on the lookout for a good harness then . Link to comment Share on other sites More sharing options...
Eagle Posted July 7, 2015 Share Posted July 7, 2015 There is no PCM on an '88 -- it's a ECU, and I don't think it feeds through the fuse panel. The Renix wiring diagrams have been posted here, somewhere. See if you can find the link. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted July 9, 2015 Share Posted July 9, 2015 PCM... ECU... Its semantics. Isn't it under the dash. I am only assuming that the wiring harnesses for each under the dash is completely different. I'm not trying to give bad information. Please correct me of I'm wrong. I've never read otherwise on this forum. Every time I read about a conversion both under hood and dash harnesses need to be swapped I'm assuming because the ECU wiring is different between the two. Am I wrong? Please don't take this as angry or confrontational. Its not. I just want to help. Correctly if I can! Link to comment Share on other sites More sharing options...
dasbulliwagen Posted July 9, 2015 Share Posted July 9, 2015 Just re read OP. Dash harness. I'm assuming again that dash harness includes EVERYTHING under the dash including the pcm,(ECU) not just section of the harness that runs the radio, lights and HVAC. Not sure which parts the OP need but maybe this should be clarified. Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 9, 2015 Author Share Posted July 9, 2015 There is no PCM on an '88 -- it's a ECU, and I don't think it feeds through the fuse panel. The Renix wiring diagrams have been posted here, somewhere. See if you can find the link. I've searched the forum for wiring diagrams , harnesses , pin outs but have found nothing relevant as of yet . All that comes up are HO swap diagrams/pin outs . Not saying they are not on here , just that I haven't found them yet . If anyone could post a link that would be great . Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 9, 2015 Author Share Posted July 9, 2015 PCM... ECU... Its semantics. Isn't it under the dash. I am only assuming that the wiring harnesses for each under the dash is completely different. I'm not trying to give bad information. Please correct me of I'm wrong. I've never read otherwise on this forum. Every time I read about a conversion both under hood and dash harnesses need to be swapped I'm assuming because the ECU wiring is different between the two. Am I wrong? Please don't take this as angry or confrontational. Its not. I just want to help. Correctly if I can! Thanks and I will take any and all advice that I can . To be as descriptive as I can : they are both 88s that do have the c101 connector on the firewall . I need the harness that is in the engine compartment that mates to the fuse box / dash harness at the firewall and goes to the front lighting harness and also has the a/c ,fuel pump and the other 2 relays ,not the c101 harness or injector harness . I haven't been able to check to see if the ECU plug is the same or if it's even part of the harness I described above . I don't want to go out and buy another harness if the 2.5 harness is the same but have no issues if I have do end up having to buy one .I Appreciate the help and am sorry if I caused any controversy . Link to comment Share on other sites More sharing options...
cruiser54 Posted July 10, 2015 Share Posted July 10, 2015 I'm thinking you'll be fine from C100 out to the engine bay. I've got a c100 to engine bay harness removed from an 87 4.0 Cherokee out in the garage. How can I help? Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 10, 2015 Author Share Posted July 10, 2015 Here is a picture of the harness ends of the 2.5 harness that I'm going to try to use on my 4.0 if it is in fact the same . Does it look like your 4.0 harness? If it's not the same then I'm just going to look for a 4.0 harness( I'd rather not have any spliced wires ). Can I grab a harness out of an 89 xj / mj ? And while I'm at it , grab and change the rest of the harnesses in the engine compartment to eliminate the c101 ? Thanks Cruiser Link to comment Share on other sites More sharing options...
mjeff87 Posted July 10, 2015 Share Posted July 10, 2015 FWIW, I swapped a 4.0 into my 87, which was a 2.5 (with C101 under the hood). I used a 4.0 underhood harness from an 89 MJ, plus the ECU from same. After much research, I determined that the cab harness was nearly identical between the two, and everything worked 100% except I had to install a new HVAC fan motor because the 89 harness had a different connector (I could have spliced the wires but didn't). The 89 harness did NOT have the C101 connector, the wiring to the ECU ran thru a grommet in the firewall (already there). The ECU is not a part of the cab harness, at all. HTH, Jeff Link to comment Share on other sites More sharing options...
cruiser54 Posted July 11, 2015 Share Posted July 11, 2015 I'll try to dig mine out soon. Kids moved back in with us and put a huge couch and other crap right behind the door to my shed. I can't get to nuttin!!! Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 13, 2015 Author Share Posted July 13, 2015 I'll try to dig mine out soon. Kids moved back in with us and put a huge couch and other crap right behind the door to my shed. I can't get to nuttin!!! Don't go out of your way , but I appreciate the offer !! I may just try to locate a harness from a jy or post a wanted ad on here . I was thinking that someone had already tried or done this . I'm going to search for an 89 mj / xj 5spd 4.0 harness because it won't have the c101 and should work being the ECU s are interchangeable from 87-90 like you pointed out . Link to comment Share on other sites More sharing options...
Strokermjcomanche Posted July 13, 2015 Author Share Posted July 13, 2015 FWIW, I swapped a 4.0 into my 87, which was a 2.5 (with C101 under the hood). I used a 4.0 underhood harness from an 89 MJ, plus the ECU from same. After much research, I determined that the cab harness was nearly identical between the two, and everything worked 100% except I had to install a new HVAC fan motor because the 89 harness had a different connector (I could have spliced the wires but didn't). The 89 harness did NOT have the C101 connector, the wiring to the ECU ran thru a grommet in the firewall (already there). The ECU is not a part of the cab harness, at all. HTH, Jeff Thank you for the info , the harness I'm changing is in the engine compartment not the cab . It's good to know I can reuse the cab harness if I do locate the non c101 harness . Link to comment Share on other sites More sharing options...
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