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E32 750i 6 speed swap - guys please help with the electrical!!!

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    E32 750i 6 speed swap - guys please help with the electrical!!!

    I know someone out there knows what's going on...

    I'm helping a friend with his 6 speed 750i swap and it's acting up. The swap is physically done but with the stock cluster it's in limp home mode - won't rev over 2 grand. We tried a few other clusters, a 535i (won't light up) and an M5 - which let it rev to 6 grand but it ran richer than hell and wouldn't let us scan codes. I'm guessing it ran too rich because the rpm pulse the M5 cluster sends out is 2x too high (ie the V12 cluster reads a pulse from one coil so the rpm needs to be doubled by the DME).

    Can anyone please help us out? What the hell is it in that damn cluster that is making the DMEs think that the transmission is broken and throw it into limp home? Why does the M5 one not make it care? The trans ECU is disconnected so there are no more remains of it...

    #2
    I have some experience working on issues like this on a swapped e34. The limp mode annoyance was removed by grounding a pin on the transmission computer harness. Sorry I don't recall what one.
    Tenured Automotive Service Professional - Avid BMW Enthusiast

    Vapor Honing & E30 ABS Pump Refurbishment Service
    https://mtechniqueabs.com/

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      #3
      Originally posted by Jordan View Post
      I have some experience working on issues like this on a swapped e34. The limp mode annoyance was removed by grounding a pin on the transmission computer harness. Sorry I don't recall what one.
      Awesome, thanks a lot man! I'm not shy of doing the leg work but there are just so many things it could be and I don't have the logic schematics of the computer internals so it's kinda like a blind one legged guy on a quest up the mountain - don't even know where to start.

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