Wait Detection Switch
WARNING: This page is about a different car, the 2004 Nissan Titan. However, it is still accessible from the selected car via links, so may be relevant.
It detects that transfer gear is in 4WD by 2-4 shift fork position.
NOTE:
If 4WD shift switch is switched to 4H or 4LO, transfer is not in 4WD completely when gear does not engage. (Wait detection system is operating.)