I had a weird issue in the car the other day
I was using the USB plugged into a Fiat 500 which has the Blue & Me system. I wasn't particularly bothered about having sound through the speakers, I just wanted to charge.
The stereo turned on anyway, and I was having random directions given through the stereo, with the Highlight Video music in between!! And then the ACTUAL directions coming through the phone speakers. I just turned the stereo off but it was really weird