I recently purchased this car, and the audio system doesn't work. The head unit will come on, and stay on for about thirty seconds, then shut off. It will play no sound, will not scan through stations, and will flash something to do with "System Unavailable." The gentleman I purchased the vehicle from pulled a blown fuse from the fuse box below the passenger side rear seat, which I promptly replaced. Nothing changed. Aside from that, the display on the gauge cluster says that the SOS is malfunctioning. The doors also don't lock with the buttons on the door or the key fob, and the trunk will not pop with either button as well. Anybody have any ideas how I can fix these myself? Nearest Benz dealership is literally across the state, would rather not take it there for them to work on if there's any possibility I can do it myself.