WARNING: This page is about a different car, the 2003 Infiniti I35. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Engine Cooling System Overheating Cause Analysis Chart (1 Of 2)
Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Engine Cooling System Overheating Cause Analysis Chart (2 Of 2)