I've had my 2009 GT for less than a week, so I'm still discovering new things about it. Today I discovered a hiss from the stereo that, once noticed, is really annoying. It's the OEM stereo so there shouldn't be any amp compatibility issues or ground issues. It's at a constant volume no matter how high or low I adjust the volume. It's there for all modes (FM, AM, XM, Aux).
Any ideas what's causing it or how to get rid of it?