We have a 2007 TL, which we bought brand new and which has less than 60,000 miles on it. I recently had a dead battery. After I installed a new battery, I took it into the dealer for an oil and filter change. When I picked it up, my navigation screen appeared but I was unable to activate the audio screen. I'm sure it was due to the dead battery but the dealer activated the navigation system using the code, but when I try to switch to audio, nothing happens. Any ideas?