Audio System Symptom Troubleshooting - Audio unit button illumination does not work
  1. With the headlight switch still on, check for voltage between audio unit connector A (17P) terminal No. 10 and body ground.
Is there battery voltage?
YES -
Check the connections at the audio unit connector A (17P). If all the connections are OK, replace the audio unit.■
NO -
Repair the open in the wire between the under-dash fuse/relay box and the audio unit.■