All the functions on the radio, nav, phone etc work, however, no audio. Dealer claims it is the radio?? Others say it is the amp. Dealer wants $3000 just to replace the radio. One observation was that the sound would work everyother time the truck was started which leads me to believe it was a loose wire. Since the dealer looked at it, it doesnt work at all.
I just finished talking with the techs at my dealer re: your problem. Unfortunately, it can be eithr the radio or amplifier, but most likely the radio. The problem with the amp is did they check to see if the amp had voltage coming into it and going out. If not, it's the amp. Otherwise it's the radio.
Re: the $3,000., the dealer thinks they must be trying to charge you for the whole Navigation unit when it is not neccessary. Only the radio needs to be replaced, and here it runs $750. installed. Cost vary quite a bit from dealer to dealer as you go around the country,and maybe your local people are have higher overhead? (huh?)
I don't know if this helps but wanted to give you some facts instead of more speculation.