Using an Android device and looking for a way when my device is connected via Bluetooth to have Google Maps directions come out of the speakers. Have no issue with music over Bluetooth but can't get Google Maps audio going. I'm in a 2017 C-5 GT.
It depends a lot on the phone. Different phones treat some BT connections differently. Some phones have advanced BT settings that let you tweak the BT settings, but most don't.
There is also a setting in the Nav settings:
Maps- 3 bar menu left - settings- scroll down to Navigation settings - Play voice over bluetooth
Personally i don't like it as it interrupts my music - I want it to come out of the phone.