I have an '08 Escalade 41CKS, but I am not sure where the switch in the basement is that you are referring to.
In the basement, I have two switches: one is for the light and one is for the speakers.
In the basement, I have one switch for the basement light on that side.
In the LP compartment, I have the obvious switches for the landing gear.
In the water hook-up compartment is a switch for the light in there.
2006 Volvo VNL 780
2008 K-Z Escalade Sportster 41CKS
2001 Honda XR650R and 2018 Kymco Spade 150