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2.5 - 4.0 swap wiring question

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i'm swapping a 90 4.0 and 87 aw-4 into my 88 2.5 ax-4, and i have a question about the wiring... i'm mixing 87 and 90 wiring harnesses, are any of the plugs different between the two? the harness with the ecu and tcu plugs that runs into the interior is from the 90 (4.0 aw-4), and the other harness that wraps around the front of the radiator support and connects to the starter solenoid and all the plugs over by the battery is from an 87 (4.0 ax-15)... and also there is a 6 pin plug on the 90 harness thats under the dash next to the plugs for the ecu that doesnt match anything else there, i was curious as to what that plug is for... any help is appreciated, thanks!

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Short and simple solution............


Change all the wiring harnesses.


The '90 is still the Renix era, BUT.......the 2.5 to 4.0 is entirely different.


You need to change out the engine harness, the dash harness, including the fuse box, and the ECU, plus add the AW4 controller under the dash, so the simple problem solution, is to swap over ALL the wiring, controllers, and do-tads to make it simple and operational when your done.


That 6 pin connector your asking about, should be the AW4 controller.


Plus, changing from a 2.5 to a 4.0, you need to change out the radiator and the radiator support.


The only harnesses that you can keep and reuse, are the rear harness for the fuel pump/tail lights, and the front header panel, lites harness.


You know, there are countless topics on this subject, most can be found in the DIY section ;)

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