98 GT with 2003 Mach 1 swap. Harness questions and direction

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  1. #1

    Default 98 GT with 2003 Mach 1 swap. Harness questions and direction

    I recently picked up a 98 GT that had an incomplete 4v swap with a 2003 Mach engine. The prev owner did most of the hard work but I am finding some problems with the wiring. So the swapped in the engine and pulled in the Mach PCM harness. Here is the issue: the 2003 PCM harness does not mate with the 1998 dash harness. I am looking for the easiest route from here.

    I have:
    Mach engine in with Mach engine harness
    Mach PCM harness in with a 2001 Cobra PCM

    I got in the purchase the following extra harnesses:
    1998 GT PCM harness
    1998 GT PCM
    2003 Mach underhood power supply harness
    2003 Mach dash harness / fuse block
    2003 Mach full body harness

    From all I read, I need to either go back to the GT PCM and engine harness with the GT PCM or I need to install the Mach dash and body harness. Is this true? I am hoping I can look at the harness pin outs for the Mach PCM harness and 1998 GT dash harness and repin some connectors.

    Any thoughts or direction are appreciated!

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  3. #2


    Seems almost impossible to get a a response from people in this sub forum eh.

  4. #3


    Probably just not a lot of folks with your particular components combination.

    Your initial assessment about dropping back to the original ECU or upgrading to the later dash are the correct if not easily accomplished paths to follow. Considering the limited CPU speeds in those older ECU's you would be better off going with current technology and fitting it or keeping your original ECU for the dash etc and going aftermarket on an engine only ECU like MS3Pro Ultimate <=clickable.


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  6. #4


    Thanks for the thoughts! At this point, I am going to go back to 98 wires and ecu. It seems the easiest and cheapest.

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