A 2003 X5 would be pre-wired for phone or Bluetooth. But, it would not typically have Bluetooth unless a previous owner installed it as a retrofit. If you push the R/T button on the steering wheel or the telephone button on the MID, does the phone option appear on your screen. Or, if you have navigation, do you have navigation, do you have a TELEPHONE option on the main menu. If not, then you do not have Bluetooth installed.

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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