2000 740il radio has no sound
radio displays on my dash as well as the CD changer. the car has a Nav system. the problem is i can see that the radio works but i am not getting any sound at all thru the speakers. the car battery was replace with a new one. my old BMW "5" 94 if you replace the battery you had a code to press in to reset it. this one does not. even the Nav screen is white. the car was brought used and is in good condition except the radio. do i need to go to a BMW dealer? or is there something i can do myself to reset or fix this problem?