iPhone 13 Google Maps audio not through car speakers

I have a Toyota Touch 2 in my car that is bluetooth paired with my Iphone 13. Plays music perfectly throught the cars speakers. However when I then activate Google Maps on my iphone and use it as a Satnav device in my car, I have interwork problems. Essentially, when Google Maps wants to give me directional advice, the music coming from the cars speakers is muted, and instead I get directional advice from my iphones speaker(s) along with the music thats still playing (you can't hear the directional advice).

I had hoped that correct operation would have been music muted, satnav advice allowed through the car speakers, then resumption of music from where it had left off. But I have never to date, had the setup working in this fashion.

Anyone else in a similar predicament ?

If it helps, the software version of my Toyota Touch 2 is 01015B, and my ios on my iphone 13 is 18.7.2