Retained accessory power, I believe it's 10 minutes. Same with headlights turning off I believe..
The radio has Batt power connected all the time, but the BCM? sends a signal to turn it off I believe..
So when you hit the power button, it sends a signal to the BCM that then sends a signal back to the radio to turn on.. makes perfect sense!
You could wire up this device I have.. a PAC-LAN29ON, discontinued..
https://catalog.pac-audio.com/catalog/specialty-items/lan29on
I believe it's to simulate the GMLAN signal to turn the radio on or off, otherwise the radio won't turn on by itself! (From what I read, have not tested)
Perhaps you can wire a switch to the GMLAN signal wire and disconnect it after turning on?
BUT, when you actually want to turn it off.. it may not work
(Short of cycling your key back on and off maybe?)
Or it may not work at all.. Or go aftermarket stereo..
Like all the electronics in our trucks, way too much work for nothing!
Don't think I'll get anything newer when it's already this ridiculous in '07...
He probably meant, Read The Factory Manual, right?