More likely the phone is failing to present itself as removable storage, which is what the head unit would expect.I would use the 12V to get 2A to charge phones. Most new phones can take on 2A. I notice if I plug my phone in the usb port sometimes the head unit would freeze. Now that I don't use the usb port to charge phone. The freezing of the head unit doesn't happen. Wonder if my phone is trying to draw more than it can output.