Audio System Symptom Troubleshooting - Volume does not change
  1. Check for continuity between the terminals of audio unit connector C (12P) and audio/navigation switch panel 24P connector according to the table.
    From terminal
    To terminal
    Audio unit connector
    Audio/navigation switch panel connector
    C4 (GRY)
    No. 1 (WHT), No. 13 (BLK)

Is there continuity between any of the terminals?
YES -
Repair short in the wire(s) between the audio unit and audio/navigation switch panel (replace the appropriate shielded harness).■
NO -
Substitute a known-good audio unit and recheck. If the symptom/indication goes away, replace the original audio unit. If the symptom is still present, substitute a known-good audio/navigation switch panel and recheck. If the symptom/indication goes away, replace the original audio/navigation switch panel. ■