1. Check for continuity between navigation unit connector B (14P) terminal No. 12 and the audio unit connector A (20P) terminal No. 12.

Is there continuity?

YES | - | Go to Step 10 .
NO | - | There is an open in the circuit between the navigation unit and audio unit. Check for poor connections or loose terminals at the audio and navigation units. If a poor connection or loose terminal is found, replace the affected shielded harness.■

1. Substitute a known-good audio unit, and recheck.

Is the system OK?

YES | - | Replace the original audio unit.■
NO | - | Replace the navigation unit. ■