97 cavalier stock cd deck

my sis changed her stock cd player outta her cav and put in a new one..and but now its got that lock on it..and i wanted to put it in my dads sonoma anyone know how to unlock it? cause i know the dealer will think its stolen or something if i brought it there in a truck and not a cav

The unlock code should be in the manual of your issters car. Usualy on a little card the side of a credit card. atleast thats the way the honda's are.

get the serial number off the radio and the vin off her cavalier...call the dealership and tell them you replaced the battery in her car and it coded the radio, they can look it up by that information