Diagnosis Function

WARNING: This page is about a different car, the 2005 Nissan Altima. However, it is still accessible from the selected car via links, so may be relevant.

It can check for continuity of the switches by sounding the beep(s) when each audio unit switch (without NAVI) or AV switch (with NAVI) and steering switch (with NAVI) is pressed.
It can check for harness continuity between AV switch and steering switch (with NAVI).