So my son plugged his phone into my mazda 2 2012 via the aux cable. All worked fine. Plugged it in the next day and it won't work. It says phone on the screen and the volume controls work but there is no sound and I can't select CD or the radio. Even when he plugs his phone in again it does not work. Any ideas welcome. I've tried taking the battery off but that makes no difference. Is there a way to totally reset the stereo?