Sounds like you have er cased pretty good. The only possibility i can think of is with my truck and the nav is as soon as you get above 5-10kmph it locks the gps so you can not change it. but when you slow down to a near stop it allows you to edit the gps. Maybe there is something to do with that wire that picks up your speed to lock the gps is also the wire in your situation that is shutting down your stereo. sort of doing the opposite. I do alot of stereo wiring aswell and it sounds like you have done it all. This is sort of just a shot in the dark since the speeds are the same.
I don't think its Alternator dropping amps because you say it comes on after you sit a bit at an idle. What about hooking up your constant power from a different source other then the factory location. You said you hooked it directly to the battery.... what was the results? Did it still shut off?
Maybe it is actually the radio with the issue and not the truck.
Good luck.
I don't think its Alternator dropping amps because you say it comes on after you sit a bit at an idle. What about hooking up your constant power from a different source other then the factory location. You said you hooked it directly to the battery.... what was the results? Did it still shut off?
Maybe it is actually the radio with the issue and not the truck.
Good luck.