Was reading through the 07/08 manual today and noticed this little gem for folks that use non-stock antennas:

Howto check for audio system condition

NOTE: The audio unit must not be in the code enter screen before performing the self-diagnostic function.

1. Turn the ignition switch to ACCESSORY (I) or ON (II).
2. Turn OFF the audio unit.
3. Push and hold the No.1 and No.6 buttons. While holding the buttons, push the VOL/PWR knob to ON. Release
the buttons and the self-diagnostic function begins.

4. By pressing a preset button, the input will trigger the diagnostic mode that is assigned to that preset switch.

No.3 button
Entire LCD lighting/light-out mode: Turns on/off the entire LCD to show the presence or absence of an LCD failure

No. 4 button
Duty (for the Illumination dim) indication mode: Indicates the duty for the Illumination dim.

No.5 button
Vehicle speed pulse indication mode: Indicates the vehicle speed pulse.

FM button (Push and hold 5 sec.)
Reception level check mode: Indicates the reception level.

5. The self-diagnostic function will end when the audio unit, or the ignition switch is turned to LOCK (0).


Using the FM button test you can compare the signal quality of a radio station with different antennas. The higher the number the better the signal.