Audio switch panel button illumination does not work

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2017 Honda Odyssey, 2016 Honda Odyssey, 2015 Honda Odyssey, 2014 Honda Odyssey, and 2013 Honda Odyssey. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Check the vehicle battery condition first (see BATTERY TEST ).
Check the connectors for poor connections or loose terminals.

Turn the ignition switch to ON (II).
Turn the combination lighting switch to the parking light position.
Check the illumination of the audio switch panel buttons.
Are the buttons illuminated?

YES -Intermittent failure, the audio switch panel is OK at this time. Check for loose or poor connections at the audio unit connector A (24P).

NO -Go to step 4.
Check the illumination of several other buttons not related to the audio system.
Are the buttons illuminated?

YES -
- Without USB adapter 1 line display type: Go to step 5.
- With USB adapter, or without USB adapter 3 line display type: Check for B-CAN DTCs (communication BUS Line Error) with the HDS and go to the indicated DTC's troubleshooting.
  If no B-CAN DTCs or communication bus line errors are found, substitute a known-good audio unit (see AUDIO UNIT REMOVAL/INSTALLATION ), and recheck. If the symptom/indication goes away, replace the original audio unit (see AUDIO UNIT REMOVAL/INSTALLATION ).
NO -Troubleshoot the interior lights. Start by checking the No. D25 (7.5 A) fuse in the passenger's under-dash fuse/relay box. If the fuse is OK, check for an open in the wire between the passenger's under-dash fuse/relay box and the audio unit.
Turn the combination lighting switch to off.
Turn the ignition switch to LOCK (0).
Disconnect audio unit connector A (24P).
NOTE: Eject all the discs before disconnecting the audio unit to prevent damaging the CD/DVD player's load mechanism.
Turn the ignition switch to ON (II).
Turn the combination light switch to the parking light position.
With the combination lighting switch in the parking light position, measure the voltage between audio unit connector A (24P) terminal No. 4 and body ground.

Fig 1: Measuring Voltage Between Audio Unit Connector A (24P) Terminal No. 4 And Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Go to step 11.

NO -Repair an open in the wire between the passenger's under-dash fuse/relay box and the audio unit.
Turn the combination lighting switch to off.
Turn the ignition switch to LOCK (0).
Disconnect the gauge control module 32P connector.
Check for continuity between audio unit connector A (24P) terminal No. 2 and gauge control module 32P connector terminal No. 15.

Fig 2: Checking For Continuity Between Audio Unit Connector A (24P) Terminal No. 2 And Gauge Control Module 32P Connector Terminal No. 15
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?

YES -Check the connections at the audio unit connector A (24P). If all connections are OK, replace the audio unit (see AUDIO UNIT REMOVAL/INSTALLATION ).

NO -Repair an open in the wire between the gauge control module and the audio unit.