when you put a MP3 disc in for the first time, it takes it a little while to load, but just be patient and it should work, if the changer is incompatible then it will just give you an unplayable disc error - but wait a little bit, if you think you've waited a long time, wait a bit longer.

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2006 BMW X5 4.8is Lemans Blue/Beige/Dark Maple
-Nav, Comfort Seats, Heated Steering Wheel,
Rear Airbags, AUX Input
2009 BMW M3 Space Grey/Black/Carbon
-all options