It is a 5 digit code that came with the vehicle and was written on 2 plastic cards. Look for these cards or look for the code written in the owners manual. Without this code you will have to have the Radio Serial # in order for your Honda Dealer to provide the code, unless the selling dealer stored the code in their system. To get the radio serial # you must remove the radio from the car and look on the side or top of the radio. One other way that may work if the radio is already locked up. Press preset buttons 1 and 6 at the same time. Turn on radio. An 8 digit serial number will appear on display. (if stereo was locked up at the time). Be sure to include the "smaller" digits!