Self-diagnosis mode

WARNING: This page is about a different car, the 2013 Nissan Armada. However, it is still accessible from the selected car via links, so may be relevant.

Press the "BACK" switch and the "UP" switch within 10 seconds after turning the ignition switch from OFF to ACC and hold them for 3 seconds or more. Then the buzzer sounds, all indicators of the preset switch illuminate, and the self-diagnosis mode starts.
The continuity of each switch and control dials (A/C and AV switch assembly only) at the ON position can be checked by pressing each switch and turning each control dial. The buzzer sounds and LED's will illuminate if the switch is normal.

Fig 1: Locating "Back" And "Up" Switches
Courtesy of NISSAN NORTH AMERICA, INC.