How do I find the serial number on my 2003 Honda Accord Audio system ?

With the radio off, hold the #1 and #6 buttons down and turn on the radio. It will display 2numbers proceeded with a letter such as C1234 D2345. Right these numbers down. The numbers without the letters is the serial number. In the example above the serial number would be 12342345.

If that does not work your only option is too remove the radio and retrieve the serial number from the tag affixed to the radio.