Button Check Diagnostics
WARNING: This page is about a different car, the 2012 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.
When all segments are illuminated, press the "TUNE" down switch to enter button check diagnostics. When each audio unit switch is pressed, a tone will sound and the switch name will be displayed.
Courtesy of NISSAN NORTH AMERICA, INC.