I have a 2004 Deville DTS, recently, I have the in-dash, DVD, NAV system, I pulled up to my shop for work, shut the car off. The stereo worked fine. After eight hours of work, came out, started the car, nothing, no power, no screen, has not come on since. Checked the "Audio" fuse, not blown. I have a set of sub woofers in the back with an external amp, but its wired through the back sub, with an inline output rca adaptor. Just wondering if anyone has had any issues like this. If someone has some "Troubleshooting" advice. I don't even know where to start. The only other thing I've noticed different, is the rear sensor used to beep, or make an alert when going in reverse, and of course when you approach something, and it doesn't seem to be doing that anymore. Not thinking that should have anything to do with it. If the head unit turns out to be bad, any advice on where I might possibly purchase a new, or used one.