Diagnosis Function

WARNING: This page is about a different car, the 2003 Nissan Murano. However, it is still accessible from the selected car via links, so may be relevant.

It can illuminate all the indicators (LED) in the A/C and AV switch.
It can check for continuity of the switches by sounding the buzzer when the A/C and AV switch is pressed.
It can check for continuity of harness between A/C and AV switch and steering switch (audio).