Help,have a 05 nav,9months ago 4wd indicator was flashing on dash all the time although truck would engage 4 high or low as selected.searched the forums and found others with similar problems and had local mechanic change the three switches on the transfer case,problem solved.4weeks ago same problem returned although this time I can not select 4wd at all.took back to mechanic who said switches looked fine and sent truck to auto elec.auto elec says he can not access Nissan computer to diagnose fault.says Nissan is the only manufacture that they cannot access.truck must go to Nissan,does this sound right?