CLARION are a bit of a problem to decode as the only one that can be decoded for free by Serial Number is if yours also has a BARCODE SERIAL NUMBER beginning with C7000000 + + + + .
If yours does not have this C7000000++++ Serial Number anywhere on your radio then you will have to pay at your Main Dealer or a Decode Specialist.or a local Car Radio / Audio Shop who carry out decodes ( The shop is usually the cheapest option)