2.5L and 4.0L under dash wire harness interchangeable? - JeepForum.com
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Unread 04-22-2010, 05:05 AM   #1
aaron0000934
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1989 YJ Wrangler 
 
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2.5L and 4.0L under dash wire harness interchangeable?

Well I guess the title says it all. I have swapped a 4.0L out of a XJ into my 89 YJ. I am using the XJ harness under the hood. I am running a in tank fuel pump and would like a 92-95 under the dash harness to complete the build. Are the 2.5 and 4.0 under the dash harness the same? Does the 92-95 harness plug into the steering column connectors? I think I read somewhere that the speedo connector is different. Any thoughts would be appreciated, thanks

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Unread 04-27-2010, 10:05 AM   #2
aaron0000934
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Really no one knows the answer to this question? There has to be someone out there with this knowledge.
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Unread 04-27-2010, 10:13 AM   #3
Nitro_Man
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I was looking at my Jeep manual yesterday for electrical diagrams. Everything is pretty much the same inside the Jeep for 2.5 and 4.0. 2 main connectors, one is above the e-brake, other at the steering column.

There are a few differences in the engine compartment, but not much.
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Unread 04-27-2010, 10:17 AM   #4
aaron0000934
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perfect, thanks
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Unread 04-27-2010, 10:27 AM   #5
1990offroadYJ
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Yea i did a 4.0 into my yj with a xj motor and wiring too. i incorporated the inside xj harness and dash into my jeep for temporary because i was running out of warm weather. and i was told by a friend that the yj underdash harness out of a 92-95 would plug into the firewall of the xj engine harness.. but you will need to get 92-95 speedo and gauges to have all the same plugs. and not splice. i got all the stuff pretty cheap off of ebay i just have to do it now. and you will need to find a VSS to go into the transfercase to get the speedo to work because it is not cable driven its electronic. You also need the wiring to make it from the VSS to the engine wiring harness because it goes to the ecu and controls idle. like i said i used all the xj dash gauges except for the speedo and it stalls almost all the time when i step on the brake and clutch to slow down to a stop. if you have any questions just let me know. i did my swap it i love the power and it was my first motor swap aand it worked
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Unread 05-13-2010, 11:14 AM   #6
aaron0000934
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Well im glad im not the only one attempting this swap. I acquired a under the dash harness from a 92 YJ 2.5L jeep. I installed last night. All the connectors for the steering column were the same and also the light switch and dimmer. The heater box motor and heater controls worked too. There are a few others that I have not idea where they go. I am watching a speedo and temp, fuel, clock, guages on ebay from a 92-95. I also acquired a harness from the same jeep that goes to the tail lights. The connectors for the tail lights are different. I also cant find the connector for the fuel pump. Is that part of this harness? Also I have all the underhood harness from the XJ. I was going to use the headlamp harness from the 89YJ too. I was able to separate the XJ harness at the firewall and plug the headlamp harness in from the 89YJ. But does the other connector from the XJ control more than just the lights? hard to tell because they are all taped together. I guess i can plug it all together and see what happens. I have the harness that goes back to the tranfercase from the XJ so I think im ok there.
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Unread 05-16-2010, 09:15 PM   #7
1990offroadYJ
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the fuel pump is part of the wiringharness that goes back for the brake lights.
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Unread 07-07-2010, 09:52 PM   #8
1990offroadYJ
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did you every get the wiring done?
Im doing my wiring now and the passenger side of the connector isnt at all the same so i took out all of the wires out of the bulkhead and am putting them where they need to be.
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Unread 02-17-2014, 09:42 AM   #9
ehamilton
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I am trying the same swap but with a commanchee 4.0 from a 92 what will need to be changed. I hooked everything up and they are not the same. I currently found a 95 yj 4.0 engine wiring harness will this plug into and work with the 2.5 underdash wiring?
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