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E34 525it transmission module questions

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    E34 525it transmission module questions

    I am working on a 95 525it that will not start. The car has a transmission program message on the dash & the gear indicator will only display for a second following key on before it goes blank. When I am able to communicate with the trans module it shows no faults stored and all gear positions are read correctly. Most of the time I get no communication with multiple modules. When the communication issue is occurring the only modules I can talk to are the airbag, abs & ews module. The car can be started by jumping the starter.

    I am having trouble finding how the transmission communicates on this car. The wiring diagram shows a can bus to the DME & EGS is the cluster used as a gateway between the diag & can bus for diagnosis like on later cars? Is the gear indicator transmitted via can to other modules?

    There is an off-white/beige plastic module that sits right of the gear shift arm. When you move the arm backwards and forwards it has a built-in probe that follows the movement of the shifter arm and makes contact with different areas of a metal plate sending different levels of current back upline to allow the computer to know which gear the car is in. Sometimes that plate and the probe need to be cleaned so good contact is made at all times. Yours could be dirty or broken. One easy way to find out if it is clean or not is to turn the key one notch and put the car in R. If the backup lights come on immediately you'll know it is clean, if they hesitate or if you have to jiggle the arm or if they don't come on at all --> You have found the issue. It is easy to clean the plate off. Just remove the gearshift cover and you'll see it. Good Luck!
    Last edited by Rockabilly_Rebel; 09-21-2018, 06:04 AM.