How to Obtain the Audio Unit Serial Number

NOTE: You can only do this procedure when the battery power has been disconnected from the audio unit and the audio unit displays CODE when the radio is turned on.

Turn the ignition switch to ON (II).
Make sure the audio system is turned off.
Push and hold the preset No. 1 (A) and No. 6 (B) buttons.
While holding the buttons, push the VOL PUSH PWR knob (C) to ON.
Release the buttons and the self-diagnosis begins.

Fig 1: Identifying Preset No. 1 And No. 6 Buttons
Courtesy of AMERICAN HONDA MOTOR CO., INC.
The audio unit displays a U and a 4 digit number (A) (example U1234). These are the first 4 digits of the serial number. The display then changes to a L and a 4 digit number (B) (example L5678). These are the last 4 digits of the serial number.

Fig 2: Identifying Digit Number
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Use all 8 numbers as the serial number when using the Interactive Network (i N) to retrieve the 5 digit anti-theft code.
To end the self-diagnostic function, turn the audio unit off, or turn the ignition switch to LOCK (0).