WARNING: This page is about a different car, the 2003 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.
Check continuity between terminals of the key switch and key lock solenoid connector.
Fig 1: Key Switch Condition Continuity Chart
Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Checking Continuity Between Terminals Of The Key Switch And Key Lock Solenoid Connector