Thought I'd share a simple self diagnostic for the navi that I got from my G35 Sedan Service Manual. Any issues with their navi will quickly show up on this diagnostic.
1/ Start the car 2/ turn on the navi 3/ simultaneously push the D/N and the MAP buttons for 5 seconds 4/ follow instructions to determine if there are any probs and where they are. 5/ when finished, shut off engine, restart and drive for short distance to 'fix' navi to your location again.
This is strictly a DIAGNOSTIC procedure for info only and to be sure all the components are functioning properly within the system. Hope this helps. I've done it 3 times on mine (no probs) and works like a charm. This applies to both Sedan & Coupe Navi.
Gsedanman- Garnet Fire Sedan