How do I unlock my radio when it won't give me a code?

not sure about your car,but on the hondas,if you unhook the battery or it goes dead,you have to enter a security code into the radio because the car thinks the radio is stolen!they put the radio code on the inside of the glove box on a sticker or label.also on a little card in the owners manual.if you enter it wrong 3 times,it will lock you out for 1 hour,before you can enter it again.