alright, you NEED to listen to me. I have seen this problem before.
there is a plug not pluged in.
let me guess, the dealership installed the ipod head unit.
if you can take apart your dash you will see that there is a wide and slender hole that needs something in it in the back of the head unit. the plug is going to be wrapped in grey foam as a part of the factory wiring harness. pull off the foam and plug that connector in. then try your ipod. and it will work.
your service dept. may not know or, may not know how to check for this. the instructions are a bit unclear.
i mentioned this in various postings in this thread and others. now i am done. good luck.