Find the TCU and verify the part number. Here is a post with a listing of TCU part numbers and whether they have Bluetooth.
Here's a great TCU part number reference

The TCU is located in the rear compartment, by the CD changer and DSP amp. If you have navigation, I believe it sits above the navigation bracket.

__________________
SOLD
2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input