My 2006 X5 had the same battery drain. One weekend we didn't use it at all and on Monday morning it was completely dead. I took the vehicle to the dealer and they said it was the bluetooth TCU that would not allow the vehicle to go to sleep and therefore needed to be replaced. Instead of paying $650 to replace the module I just had them disconnect it. This was a year ago and I haven't had an issue, but yesterday after reading in this forum about cleaning the TCU connections could possibly solve the issue I decided to reconnect the TCU.
How can I tell if the vehicle goes to sleep? The bluetooth stops working when I turn of the vehicle but not sure how to tell if the vehicle is completely asleep.
Also, could the phone model have any thing to do with the TCU not going to sleep? I previously had a blackberry when the problem first occurred, but now I use a iPhone 4S and 5.