I'm not 100% sure but the USB port for the car is only for flash drives. The car will detect that its a zune just because thats the name of the drive and will also be able to "see" the files. But it will probably not be able to play them. Some MP3 players have a feature that they switch to a flash drive instead of an MP3 player once they're hooked up via USB port. That might be whats the problem. Worst case go to the dealership and ask them about it.