Intermittent "No Sound" from Cd-Changer & Phone?

I was wondering if anyone might have experienced any related problems with their audio systems? I used to have a problem where every once in a while after starting the car, I would receive a message that there was no CD-changer or phone from the stereo head unit.

After bringing the car in several times to the dealer, the PSE component and the head unit were replaced. Now every once in a while when I start the car, there won't be any sound from the cd-changer or phone while the radio will produce sound.

I have brought the car in at least 5 different times and would like to get some helpful information from anyone on this forum that might help in resolving this issue before taking the car in again since it seems the dealer doesn't know what to do either.

I would appreciate any helpful information. My email address is [email protected]

Thanks in advance!
J.P.