call them. call the dealer you bought it from. some may be able to check the database with your vin, others will need to use the serial behind the deck.

taking it to the dealer will probably end up in a $60 charge of them removing the deck, and checking the serial itself.

or you may get lucky and get it done for free.

also, the code should be written in a card with your manuals if you bought the car from the dealer.