1. Check for continuity between navigation unit connector A (20P) terminal No. 15 and the audio unit 20P connector terminal No. 12.

Is there continuity?

YES | - | Go to Step 8 .
NO | - | There is an open in the circuit between the navigation unit and the 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 shield harness.■

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

Is there system OK?

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