hello , i have the same problem , after someone from a car service has replace the battery (he said that is the only thing that he did, i dont know i wasant there ) the red led from my nav screen doesnt work and i cant access CD/RADIO and i dont have any sound of all. I try to use the handfree from the cars phone and its working but still no sound. Anyone have any idea? (the sound was working before changeing the battery)