Audio System Symptom Troubleshooting - Audio unit button illumination does not work

Audio unit button illumination does not work
  1. Turn the ignition switch to ON (II).
  1. Turn the combination lighting switch to the parking light position.
  1. Check the illumination of the audio unit buttons.
Are the buttons illuminated?
YES -
Intermittent problem: the audio unit is OK at this time. Check for loose or poor connections at the audio unit connector A (17P).■
NO -
Go to Step 4 .
  1. Check the illumination of several other buttons not related to the audio system.
Are the buttons illuminated?
YES -
Go to Step 5 .
NO -
Troubleshoot the interior lights. Start by checking the No. 14 (7.5 A) fuse in the under-dash fuse/relay box. If the fuse is OK, check for an open in the wire between the under-dash fuse/relay box and the audio unit.■
  1. Turn the ignition switch to LOCK (0).
  1. Disconnect the audio unit connector A (17P).
  1. Disconnect the gauge control module (tach) 36P connector.
  1. Check for continuity between the audio unit connector A (17P) terminal No. 1 and gauge control module (tach) 36P connector terminal No. 14.
Is there continuity?
YES -
Go to Step 9 .
NO -
Repair the open in the wire between the gauge control module (tach) and the audio unit.■
  1. Turn the ignition switch to ON (II).