New to 2012 P4. Connected old iPhone 6S (acting and seen as "iPod") with my music to car with USB in the console. I put it in airplane mode, BT off. Worked perfectly. Held a charge long enough that I didn't realize it wasn't charging. When I got in the car it picked up where it left off.

Then I synced on some more music off my iMac and it updated software and iOS. Then it didn't work as before. So, this is what I've figured out so far.

The USB port charges only when the ignition switch is on. The phone won't maintain a charge for more than a few hours. Battery life is at 91% (better than my much newer iPhone X!). I realized that I had to reset airplane mode and BT. Made it hold charge longer but not long enough. Made it lock screen after a minute. Then it would hold charge but it would not come on automatically. Setting lock screen to "never" allowed it to come on automatically but then it won't hold charge long enough. Having the screen brightness almost black helps. That's where I am now.

Anybody figure this out? Newer iOS may have screwed me. Loading music (577 songs) on to a thumb drive now.

 

Same answer -thumb drive (>1000 songs )

 

256 GB SSD drive in enclosure filled with .wav albums. None of that lossy.mp3 for me.

 

thanks for the responses. thumb drive works great.