Hi Chris,
Believe it or not I have just joined this forum just to find out how others are getting on with this issue.
I have the exact identical bike and devices you have. GS TE Ex with TFT and Scala G4 (duo). I experienced the exact same problems you have. I have been in contact with Cardo in the US and they have confirmed to me that not only does the G4 NOT connect with the BMW TFT but neither does their latest offering of BT devices.
I have on order a Sena 20S Evo (duo) after trying out my mates 20S on the TFT and Nav IV. I found that I could make calls and receive music from my iPhone 8 through the TFT to the Sena 20S... works a dream. I can communicate with my pillions Q20 and other Sena devices, but like you I am unable to receive navigational voice prompts from my Nav IV. So I guess, that leaves me in the same situation as with the G4. If I want full functionality... Rider/Pillion, Rider/Rider, Phone Calls, Nav prompts it all has to be through the Nav IV and the Sena. Which like you is not what we want as I had hoped to control the whole shebang through the bikes handlebar control wheel.
It is my understanding from my local dealer, that the only way to get (nearly) everything we want, is to purchase the BMW Communicator system and connect it to a BMW System 6/7 helmet... OucH!!!. I prefer my Shubbie C4 by miles. And even then it means I can't talk to my non BMW mates. Sucks a bit!
Unless we get any more progress on this, I think the only option is to drop the SatNav prompts through the system which will still give me Rider/Rider/Pillion, Phone Calls and Music from iPhone, through the bike's controller. At least until there is some magical software update comes along that is. Mmmm!
If anyone our there has a solution for Chris and I... Please shout!
Cheers
IanChelt
I have the Nav VI and BMW system 6 comms system and that doesn't work either. The BMW comms only has one channel. It's either TFT or Nav VI, not both. A real bummer.