No map sounds over Honda SIrius radio

This doesn't help you, but in both my Fords and my Mini, I have to be on Bluetooth to hear the turn by turn, it has always been that way. I'm not sure if you were lucky, or Honda had a way to know if Bluetooth was receiving a signal while simultaneously broadcasting Sirius, it would allow a play over, pretty cool if so.

If you go to Bluetooth in settings and tap the i, is there any setting to allow that? I seem to remember at one time, something there in CarPlay on one of my phones. The map settings has volume in the settings app, may be worth a look.

There used to be a Maps setting where you could turn ON/OFF "HFP" (Hands Free Profile). This is what allowed turn-by-turn navigation prompts to be heard while using other audio sources (like Sirius). I don't know when this was removed, or why, but explains the change you're seeing.

You might see if the setting moved to the Bluetooth profile. In your iPhone's Bluetooth Settings ... tap on the "i" next to your Honda's entry and see if there is an option there.

I see in your original post you mentioned Waze and GM.

In looking into this it seems that HFP is supposed to be enabled by default (hence the missing setting). Therefore, maybe try some of these steps:

1- Delete the Honda's entry in your Bluetooth settings, then re-pair it.

2- Same as #1, but go to Settings/General/Reset/Reset Network Settings, then re-pair.

3- Backup and restore the iPhone.

4- Restore the iPhone w/o a backup (last resort).

Have you tried Waze or Google Maps? I believe there was a time when they had a setting to support HFP while iOS Maps does not, but I'm not sure if that's still the case.

Did you try "Reset Network Settings" or "Restore"?