Hi there! When your Grundig Car 2002 model radio asks for a code after a battery replacement, it usually means the radio's anti-theft system has been activated. To get the correct code, you'll need the serial number, which you�ve already shared: GM020221246191. I recommend contacting a Grundig dealer or visiting a trusted car audio specialist who can look up the code for you. Sometimes online services can help too, but be careful and only use trusted sources. Hope this helps!