Well stating the obvious,
1. water level
2. cap and system not leaking, therefore allowing correct operating pressure
3. thermostat sticking, remove it and try again, on road going vehicle, dont leave out permantly.
4. fans working
5. blown head gasket
the number of things that can make a vehicle overheat is great, even fitting dirty great headlights on a A bar in front of grill, can prevent correct flow of air.
But 12 months old, its Nissans problem.
level, fans, thermostat, i always say, start with the blindly obvious, then work up. :?