I've run into a similar problem streaming audio from my iPhone 5 to my Lexus cth200 since upgrading to 8.2. In my case, the phone and car pair, and I can see and change tracks, but the audio does NOT stream through the car's speaker system — it plays directly out of the iPhone's built-in speaker. I've tried to correct the problem by disconnecting and repairing, and I've tried it by quitting the iPhone's music app.
The only thing I've found that corrects the problem is to power the iPhone off and on; then everything is fine. Fine, that is, until the next day when the problem repeats itself. If I make a quick stop, effectively disconnecting for an hour or so, everything is okay.
My guess is that there is a problem reconstituting the port over which audio is streamed, as opposed to the port that is used to exchange control information
In any case, it is VERY annoying!