I was so frustrated with all this I signed up for the beta, so now I'm using 9.3 beta 2.
Original issue:
When updating from 9.1 to 9.2 on an iphone 6,, my 2016 Chevy car and 2015 Chevy truck intellilink system after a phone call or HFP prompt it would switch to bluetooth music on the phone no matter what mode it was in before. Since I dont have navigation in the truck I used the SIRI and Apple maps with the HFP prompts daily, it was no longer useable after the 9.2 update, like a phone call after every HFP prompt it would always start playing bluetooth music on the phone. I went back to 9.1 when it was still signed and everything was just fine. I also did a clean install of 9.2 and re-paired the phone several times.
Made the mistake of trying the 9.2.1 update, that didnt fix anything and of course 9.1 was no longer signed so I was forced to keep 9.2.1.
Shutting off SIRI did fix the phone call going to iphone music after a call and did fix HFP prompts on the 2015 truck, it did not fix the 2016 car though.
Installed the 9.3 beta 2 yesterday and here is what I found so far:
2015 Chevy truck all seems to be working now, even with SIRI enabled. But oddly now Google maps, only when using the voice input, will switch to streaming music on the phone instead of back to the previous mode. But the HFP prompts in both Apple and Google maps both work properly - returning to the last played mode.
2016 Chevy car (with carplay), phone calls go back to last mode properly, but the HFP prompt on Apple maps is grayed out and after a bluetooth map direction it starts playing music off the iphone. Google maps using the voice input works, after speaking voice directions it returns to the last mode and HFP prompts work too. Once the iphone is activated in carplay though it looses even the grayed out HFP prompt button in Apple maps - even when disconnected from carplay. Apple maps works fine in carplay, SIRI works again and Google maps works fine with the phone unplugged from Carplay.
So in the end, 9.3 beta 2 ALMOST fixes everything for me and I dont have to lose SIRI, I can live with the way it is now. Lets see what happens the next couple updates 🙂