Not on my 98 A4. I have had to disconnect the battery for different maintenance things and every time the radio comes back on and works, without needing the anti theft code. Not sure if this is typical for a Concert type radio, but I'm glad its this way. Good thing because I don't have the code. Is this normal?

 

I dont either, but it has one... Ive heard of others that dont need to type it in, ive had the entire radio out and completely disconnected and it still doesnt ask.. Not sure why.