09-12-2012, 09:25 PM
Officially Welcomed to the 'Fest
Join Date: Feb 2012
Mein Auto: 545i
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.
Originally Posted by kskane
After some great help from CTSC, I finally figured the solenoid 4E87 is outside the trans above the top of the gear shift. In order to get to it, you have pull out the following in sequence.
1. Hazard switch
2. Panel holding the air vents
3. Front panel containing the controls to AC etc
4. Lower panel where your NAV DVD section.
5. The centre knob
6. Menu switch
7. Gear shift knob + cover + drive panel (which indicate which gear you are in)
8. The complete mid section panel.
9. Cigarette lighter holder
And now finally if you see right above the gear shift, you will see a cable going into the gear shift. That little connector wire is going into the solenoid 4E87 (picture attached). Now back to my problem. During cold start I get a warning for this solenoid not being functional and then it disappears after few minutes. I have checked the solenoid is fine to its resistance of 19-21 Ohms, and the connecting cable has the right voltage during the day time, but strangely at cold start, the cable does not have any voltage at all for few minutes thus causing that fault message.
Does anyone has any idea why the cable will not have voltage for first few minutes? Anyone good with BMW WDS and know where the current in this cable is coming from that I can diagnose further?
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.
Last edited by bimmerfan52; 09-13-2012 at 12:41 AM.
Reason: Addtl Info