Fixing the partly failed installation of a Sony Head unit I did last weekend.
1) Aha! - there is an antenna amplifier that needs power!
2) Handbrake connection? Who needs that? It turns out that Android Auto refuses to install unless it feels "safe", i.e. can sense that the handbrake is on.
So here we go again ripping out everything.
I have lived with a Chinese Android-based head unit a couple of years now, It was fun to have Waze and Spotify directly in the unit, but I hope to get a better experience with Android Auto. And at the time I wish someone has explained to me that you need a converter between a non-Bose head unit and the Bose power amp in the rear. Now I know that. Newcomers please be ware!