How to check for audio system condition

WARNING: This page is about a different car, the 2009 Acura MDX, 2008 Acura MDX, and 2007 Acura MDX. However, it is still accessible from the selected car via links, so may be relevant.

Turn the ignition switch to ON (II).
Turn off the audio unit.
Push and hold the No. 1 and No. 6 buttons. While holding the buttons, push the VOL PUSH PWR knob to ON. Release the buttons and the self-diagnostic function begins.

Fig 1: Identifying Audio System Buttons
Courtesy of AMERICAN HONDA MOTOR CO., INC.
By pressing a preset button, the input triggers 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 segment 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.

"6 Disc" or "DVD" button (Push and hold 5 sec.)

DRAM residual quantity indication mode: Indicates the DRAM residual quantity.

"AM" or "FM" button (Push and hold 5 sec.)

Reception level check mode: Indicates the reception level. When entering the reception level check mode, the AM/FM or FM button is used to change the S-METER, OFFSET, MP and USN (A/I).

"A.SEL/ROM" button

Bus line check mode: The audio communication line is checked between the DSP, EEPROM, and TUNER.