Valvetronic power supply undervoltage

I have a 2006 530xi Wagon with 105k miles on it. I keep getting the following error code: 2A3F Valvetronic, servo motor : power supply.

I checked the continuity between the connector at the VVT servo motor and the computer, and it was fine. I deleted the error two days ago then checked and cleaned the connections to the VVT servo motor and the eccentric shaft sensor. I also swapped out the VVT relay with the DME relay (they are the same part). I checked the codes again and the same error was back and apparently it had occurred 22 times in the last two days.

This makes me think that the valvetronic system isn't working at all, which might explain why my gas mileage is so bad. Does anyone have any ideas? I'm thinking it might be the VVT motor, but I don't want to start throwing new parts and $ at the problem and hope something works.

Thanks!
-Phil

Im not familiar with INPA, but IIRC with the Bav Tech tool using actual values I was checking the actual position on the eccentric shaft with a nominal position
based on throttle input. It could only be done with the engine running (I think). I had the car in accessory mode and throttle movement reads, but the Servo
stays at rest, so I had to start it after carefully putting the servo back in (scary). Remember if the Servo fails all together the throttle plate swings into action. To see if the Servo is failing slowly maybe you could check if it can go to WOT, hold steady at increments for periods of seconds with no movement, moves as rapidly as throttle inputs, and returns to rest fully. These are
just guesses as I cannot find anything regarding Valvetronic failures other than the servo just fails all together (which is rare supposedly). Maybe a Bently Manual is in order. I'm not sure if you can read values with INPA.
Good Luck

I would say it's likely the sensor. If the car runs all the way up the rev range and its getting 22 faults, i'm thinking the DME is missing info from the sensor rather than
the servo not complying in any part of the rev range. See here though:
http://www.tunetech.co.za/2011/09/08...stepper-motor/
http://www.e90post.com/forums/showthread.php?t=519577

Thanks for the info boramkiv.

I haven't had time lately to mess with the problem, but hopefully today after work. I have an idea to see if it is the sensor. If I can find in INPA where I can check the eccentric shaft position, I am going to manually turn the the VVT motor with a hex key and see if the values change. If I do see a change in the shaft position I'll assume the sensor is fine.

I did have a minute yesterday to do a little experiment. Using a hex key I turned the VVT motor clockwise until it stopped. I'm pretty sure this adjusts the eccentric shaft so the intake valves are completely closed. Then I tried starting the car, which wouldn't start. Makes sense if the intake valves are closed. Then I turned the VVT motor counter-clockwise all the way and I was able to start the car without any problem.

This is good news for me either way, thanks!
I had this crazy notion that because the servo
looks like a motor that spins around all the way,
when you install it if its too far down for closed valves
or too far up for WOT, the computer would bring it
down or up on its own. I thought that could be a way
to control idle.

That's what I was worried about when installing. You
would think as advanced as the system is it would sort
itself out on its own. There's no idle control valve so WTF!?
Leave it to BMW to keep info glued to themselves to fix.
Good that you can adjust the hex key to get it right
which I figured was possible anyway.

My nominal value is a little off from my actual value with
the eccentric shaft, but I'm idling fine and revving to redline
no problem. So I don't know why that is. Thanks for the
updates.