WARNING: This page is about a different car, the 2005 Infiniti FX45 and 2005 Infiniti FX35. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Locating Engine Serial Number Location (1 Of 2)
Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Locating Engine Serial Number Location (2 Of 2)