Audio One of the options that BMW has been promising. The head unit does support it, but the official cable is not available. However you can still install it. Get part number 82 11 0 149 389 which is the E46 cable. You then have to remove the clip from the plug. It then plugs in nicely. You then can select AUX by pressing the mode button. If you plug it in the wrong spot, the AUX option will not appear. If you use car power with your AUX device you may get a whine from your speakers. To solve this get a ground isolation block. Radio shack sells one Part 270-0054. Photo
ist zwar in Englisch,aber vielleicht hilft es