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Old 09-13-2012, 06:30 AM
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kskane kskane is offline
From DownUnder
Location: Australia
Join Date: Oct 2009
Posts: 1,089
Mein Auto: '04 525i M54 with 6HP19Z
Originally Posted by bimmerfan52 View Post
If you hadn't tested the voltage on the solenoid I would have suggested you check to see if a soft drink had been spilled into the console and the solenoid was sticking.

I assume you checked the connector and pins to make sure they were making a positive contact and didn't need to be cleaned.

The fact that you begin to receive this signal after a few minutes of warm up leads me to believe that the generation of the signal has to do with heat and expansion at an electrical connection or solenoid.

The voltage is received from the TCM or Transmission Control Module, which in turn receives the signal from magnetic valve solenoids in the mechatronics unit of the transmission. There is also interaction from the ECM.

Failure of the solenoid, TCM or any electrical connections in between can interrupt the signal.

The attached PDF is for the same transmission, but specific to a 2002 745i. It explains the operation of the MV or magnetic valve solenoids and which one controls the transmission lock solenoid.

As you dig deeper into the TCM you should be able to isolate which pins bring the signal from the transmission for the transmission lock. If the TCM is getting the signal then it is the wiring between the TCM and console or the TCM itself.

I will keep my fingers crossed for you that the problem is outside the transmission. Pulling out the mechatronics unit is not for the faint of heart and pretty high on the DIY scale of difficulty.

In the PDF the writer's problem was the solenoid was stuck in the locked position, preventing the transmission from being taken out of park. Your problem is after you put it back into park the solenoid is not returning to the locked position, thus when you start the car the next time the ECM and TCM module system checks on start up sense the solenoid out of position and you throw a fault.
Thanks for the PDF, if I look at the diagram at the bottom, it indicates 4E87 is connected directly to Ignition Switch Interlock. So how do I test that part?
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