I'm having the same problem.
I just upgraded to the 5, bought a lightning adapter on ebay and plugged it into my factory y-cable and the only function that works is charging. My music library doesn't display on idrive.
I read another thread on here where someone had luck and was able to retain all functions of steering wheel and charging. Could it possibly be the quality of the adapter being from ebay and not from an Apple store?
Very frustrating, any help is appreciated.