Audio Unit Self-Diagnosis Function (Base System): Notes

WARNING: This page is about a different car, the 2009 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.

Turn ignition switch to ACC position.
Turn the audio system off.
While pressing the "RPT-SCAN" button, turn the volume control dial clockwise or counterclockwise 30 clicks or more. When the self-diagnosis mode is started, a short beep will be heard.

Fig 1: Identifying RPT-SCAN Button And Volume Control Dial
Courtesy of NISSAN MOTOR CO., U.S.A.
When the self-diagnosis mode is started, all of the display segments will be illuminated.

Fig 2: Audio Unit Display - Segments

Courtesy of NISSAN MOTOR CO., U.S.A.