What would you expect to the DLC connector when faults with audio system?

What would you expect to the DLC connector when faults with audio system?
I would expect if it is a domestic vehicle it would show either a A0331 or A0341 code, and if it is a imported vehicle it would show code A1679 and either code A0519 or A0520. Any of these codes will help you track down if it is the stereo itself or if it is the wiring. If none of these codes are there, then the most likely problem is the audio intereference disrupter switch, either the switch has gone bad or it is taking correct readings of the alternator interference and the alternator needs to be replaced, usually unless the alternator is not keeping the vehicle running it is just the switch.