Having dealt with this issue myself for about 6 months straight ill tell you the fix was my bank1 post cat o2 sensor. This is completely contrary to what the code was saying. I'd urge you get the BMW code. I believe it translates to 235 but it might be different for your vehicle and OBD is interpreting it differently.

Sent from my SPH-M900 using Tapatalk

__________________
----------------------------------------------
2006 X5 3.0L - Schwarz Black/Truffle Brown
Stock
But I keep it clean