WARNING: This page is about a different car, the 2005 Nissan Quest. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect the rear sonar system OFF switch connector M116. Check continuity between terminals 6 & 7.
Fig 1: Checking Continuity Between Terminals 6 & 7
Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Rear Sonar System Switch Position Continuity Chart