JeepComanche89 Posted March 14, 2017 Share Posted March 14, 2017 So I am aware that in 1991 Comanches adopted the HO version of the 4.0, along with the OBD1 electronics. My question is did the 4 cylinder models in 1991 also have the revamped computer system? Any finally if I have a 1991 comanche HO motor and engine harness, would I be able to plug the HO engine harness into the crossbody harness of a 1991 comanche that currently has a 4 cylinder motor? I'm honestly at a loss because I cannot find any info, and worse I do not have either of these things to look at in person. Any help would be appreciated! Link to comment Share on other sites More sharing options...
Pete M Posted March 14, 2017 Share Posted March 14, 2017 well, I can answer the first one, the 4banger got MPFI and OBD1 in 91 just like the 4.0. :thumbsup: Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 15, 2017 Share Posted March 15, 2017 Both the 91 and up 2.5 and 4.0 XJ/MJ models were MPFI OBD1 systems. The cross-body harnesses for the 4.0 and 2.5 have different part numbers; what the difference(s) are I don't know. I doubt if they are interchangeable. There were also subtle connector differences between the 91 and 92+ harnesses, so I'd try to find a 91 XJ/MJ cross-body harness at a yard to be sure they would all be PnP. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 15, 2017 Author Share Posted March 15, 2017 Both the 91 and up 2.5 and 4.0 XJ/MJ models were MPFI OBD1 systems. The cross-body harnesses for the 4.0 and 2.5 have different part numbers; what the difference(s) are I don't know. I doubt if they are interchangeable. There were also subtle connector differences between the 91 and 92+ harnesses, so I'd try to find a 91 XJ/MJ cross-body harness at a yard to be sure they would all be PnP. Ok so I think I understand. Sounds like the 2.5 harness would not work for me. But as far as the XJ harnesses went I thought even if I got a 91 crossbody harness, it would not be plug and play into a MJ? I'm ok with eliminating wires for the rear, but its my understanding the fuel pump wiring is completely different. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 15, 2017 Share Posted March 15, 2017 The crossbody harness is up front - has nothing to do with rear lighting. Download the 91-93 Parts catalog HERE. Look in the GROUP 8 Section, ELECTRICAL, WIRING for the MJ/XJ vehicles. This will show you how the wiring harnesses interconnect. Link to comment Share on other sites More sharing options...
JeepComanche89 Posted March 15, 2017 Author Share Posted March 15, 2017 The crossbody harness is up front - has nothing to do with rear lighting. Download the 91-93 Parts catalog HERE. Look in the GROUP 8 Section, ELECTRICAL, WIRING for the MJ/XJ vehicles. This will show you how the wiring harnesses interconnect. Awesome thank you, I am going to try and navigate it now Link to comment Share on other sites More sharing options...
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