this may be unrelated to your issue but i have experienced a similar problem with my '07. on start-up, the radio would be muted regardless of how the system was performing when the engine was shut down previously. i would have to press the volume button every time i started the vehicle to unmute the system. over time i realized this "bug" was an unintentional warning mechanism that the battery was failing. i purchased the ctek conditioner/charger & i use it when the mute recurs, which clears up the problem instantly. after several uses of the ctek, this rarely happens any longer. it recurs only after the car sits unused for a long period of time.

hope this helps.

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Facts are stubborn things --John Adams