First: Check the owner's manual. If you're lucky, sometimes the dealer or former owner will have written down the security code number somewhere in the manual (inside the front cover, or on the page that describes the radio operation, are favorite places). Also check the interior of the glove compartment - sometimes the dealer will affix a sticker containing the radios serial number and/or security code, there. IF NOT: You will need to retrieve the radio SERIAL NUMBER. On SOME radios you can do this by holding down both the number 1 and the number 6 buttons simultaneously as you turn the radio on. If you have one of those radios, the serial number will appear in the tuning window when you turn it on. IF NOT: You will need to loosen the radio and slide it far enough out of the dashboard in order to read the serial number off the plate that is affixed either on the back, or the bottom, of the radio case. When you have gotten the serial number - either call the Honda Customer Service 800 number, or stop by your local Honda dealer and give them the serial number and they should be able to give you the anti-theft security code for your radio. WRITE IT DOWN SOMEWHERE WHERE YOU WON"T FORGET IT! This will happen every time the battery is disconnected or goes dead.