I just purchased a 2010 MCS which is in impeccable condition and I am absolutely obsessed with, however I cannot get the USB port to function. Using the Y cable I was able to get it to play music off my iPhone 4S once but has since not. When I plug the Y cable into my phone and the car, the phone is charged however when I select USB from the audio menu, it says ERROR. I am quite frustrated, I took my car back into the dealer (where they kept if for 2 entire days) and the did nothing! The dealer told me that they tried it with their phones and it worked wonderfully, and therefore there is nothing they can do for me. Mind you it took me 3 hours waiting in the service lobby for someone to get my car which had been ready for me to pick up for 2 days, however I was not informed during one of my previous 7-8 calls during those two days that my car was ready and they essentially did nothing. I know it is capable of working being that it did the first time i used the y cable until I turned my car off and back on again.

 

Stick a standard usb drive in & try playing music from it. That should tell you if it really does work. Make sure the drive is formatted fat32

 

Did you give that a try, Jenny? Mine wasn't working either, so I tried just a flash drive and it doesn't read that either. Now to figure out how to fix it