If you have an 05 model year then I think you automatically have blue tooth (correct me guys if I am wrong). I think all you need to do is pair your phone and there are a few articles scattered around here that instructs you as to how to do so. Good luck.

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-2006 E53 (X5 4.4) Titanium Silver, fully optioned (sports package, premium package, navigation, ride height adjustment, panorama moon roof, rear climate package). Aero kit installed plus set of staggered 20s with Diamaris tyres.