Hello

I was reading and reading here trying to fix this problem but nothing. I have a 2003 Audi A6 2.7 Quattro and after I remove the battery to place a new one, the radio stop working as usual, I read that as a theft protection they goes in SAFE MODE until you enter the code, but my radio does not says SAFE MODE, I can change the radio station with the round button used for that and turn on and off the volume but the preset buttons do not work, I can not put a CD and not even a tape. I also read about to press RDS and PSCAN at the same time to imput the code and tried but nothing, tried with RDS and SCAN, RDS with CD, RDS with MENU, ETC but still nothing, drove it for more than 700 miles and let the engine on for more than one hour consecutive and nothing, that is why I NEED HELP you can see the radio stations in the display and also says RDS OFF

Thank You in advance for your help