DTC P1810: 4 Lo Switch: Description
WARNING: This page is about a different car, the 2012 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
The 4LO switch detects that the transfer case is in 4LO range. DTC P1810 will set when an improper signal from the 4LO switch is input due to an open or short circuit.