Audio Unit Button Illumination Does Not Work

Turn the ignition switch to ON (II).
Turn the combination lighting switch to the parking light position.
Check the illumination of the audio unit buttons.
Are the buttons illuminated?
1. YES - Intermittent problem; the audio unit is OK at this time. Check for loose or poor connections at audio unit connector A (20P).
2. NO - Go to step 4.
Check the illumination of several other buttons not related to the audio system.
Are the buttons illuminated?
1. YES - Go to step 5.
2. NO - Troubleshoot the interior lights.
Turn the ignition switch OFF.
Disconnect audio unit connector A (20P).
Disconnect the gauge control module (see GAUGE CONTROL MODULE REPLACEMENT ).
Check for continuity between audio unit connector A (20P) terminal No. 19 and gauge control module connector B (18P) terminal No.9.

Fig 1: Checking Continuity Between Terminal No. 19 Terminal No. 9
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Go to step 9.
2. NO - Repair an open in the wire between the gauge control unit and the audio unit.
Turn the ignition switch to ON (II).
With the headlight switch still on, check for voltage between audio unit connector A (20P) terminal No. 9 and body ground.

Fig 2: Checking Voltage Between Terminal No. 9 & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Check the connections at the audio unit connector A (20P). If all connections are OK, replace the audio unit (see AUDIO UNIT REMOVAL/INSTALLATION ).
2. NO - Repair an open in the wire between the relay control module and the audio unit.