Hey so I've been having issues with my navi acting up and asked my dealer to fix it under warranty and they showed me this little trick to test your system. I didn't see this posted anywhere else and it's not in the manual so I thought I'd share. Enjoy!

The navigation system has an on-board electrical system self-check feature. This check is not found in the WSM or owner's manual. The information may be useful when troubleshooting system faults N includes antenna / wire continuity checks, speed sensor signals, accy. voltage N GPS information. (Signal quality, LAT/LONG)
See repair procedure below for accessing system tests.
1. Turn ignition switch to ON position N access NAVI menu. 2. Select "SET-UP" screen from NAVI main menu. 3. Select "SYSTEM INFORMATION". 4. Select "VERSION". 5. Push joystick switch forward 2X quickly, immediately followed by pulling joystick switch back 2X quickly. 6. Information regarding wire continuity N various inputs can then be checked.