If your radio has been disconnected from your battery for whatever reason, then you’ll need to enter a Radio Code to use your radio again. In some countries, a trip to the nearest Honda dealer will suffice, but at times, dealers may provide you the radio code via phone if you provide them your car’s Serial Number (S/N). I performed the following steps to obtain my car’s (Honda Fit/Jazz 2007) S/N number (as I couldn’t find it anywhere in/on the car).
Turn your ignition key to the position wherein the radio may be turned on, but your engine does not start.
Ensure your radio is off.
Press preset buttons 1 and 6 together and while these buttons are pressed, turn your radio ON. And voila! Your S/N will be displayed on the radio’s display.