autobox wiring fault/trans prog

[agriffo]

Hi Folks,
my 1991 e34 525 has the dreaded trans prog fault. The fault codes indicated speed sensor problems but on inspection it turns out there is nothing wrong with the speed sensors, but the 'box internal wiring harness is fried, or more accurately, boiled! I have only just bought the car, knowing it had this fault, but the previous owner has been driving it like this for some time, regardless.
My questions are:
What would cause the internal 'box wiring harness to disintegrate?
Has driving the car, stuck in 'limp home mode', damaged the gearbox?
Although the car was very cheap, I obviously don't want to spend a fortune on fixing this fault.
ta
Ade

[632 Regal]

First thing I would do if I was you is disconnect the battery for an hour or so to reset all the computers and then let it idle for 5 minutes and go for a drive. If you still get a warning chime in and we can diagnose it closer to whats going on...maybe...lol

[George M]

Jeff...if his TPU is fried....it ain't gonna reset period. My guess is your car was in deep water to induce a big voltage spike into the TPU...only a guess of course because it is very rare indeed that a TPU will fry in one of these cars...an anomally. If the box is toast, you want to look for a replacement box from an equivalent car. You have to be a bit careful because BMW changed auto trans computer box calibration repeated throughout the E-34 model run specific to engine and trans. I would double check all trans sensors leading to the box before installing a new one. You can check current with a multimeter for inputs to the TPU from the trans per Bentley. I would contact board expert Kirt Koeller...contact infor in board archive for advice on what to diagnose prior to installing your replacement trans computer (TPU).
HTH,
George