No Volume Available when iphone docked to car sterio?

Hi all, this is diving me crazy. I have an I Phone 4G an I pod a Pioneer AVH P3200BT "head unit" and the compatible CD-IU50V Pioneer cord as well as the white I Phone cord. When I connect the I phone using any app ex Pandora or You Tube I get no sound over the head unit and the message @ the bottom of the i phone that says "volume not available". Also I get no recognition from the head unit as to station or song information. I have reset both the I phone and the stereo several times. When I plug in the I pod using either cord to the head unit the i pod plays as it should and song information is displayed on the head unit. According to Pioneer and their online advertisements my I phone and head unit are compilable, I have confirmed this with their representatives on the phone. I have the correct cable and it works. When I switch my head unit to auxiliary I get You Tube video but no volume with the I phone but nothing in I pod mode where it should be working. Pioneer said their are no adjustments on the head unit to make "just plug and play". I have checked my mute button on the phone several times and that is not the issue. Again I get volume and proper functions with the I pod. Does anyone know how I can fix this problem. I have been trying to find a solution for days. Thank You

Fixed partially, my pandora is now working. I had never used the ITunes app before. I somthing called goldbarradio in the itunes section it is now in my music section. Now Pandora works perfect. Does anyone know of another app I can download to get Youtube working? The volume now works w/ youtube in the Ipod section of my Pioneer sterio but no video. Video works in the auxilary section but no sound?