Tips on tracing wires from a switch

Any tips or tricks to tracing where a switch leads to?

Have a dump valve switch on the dash of my 05 379. It's a factory installed switch and has a red light that comes on when it is switched on.

I tested the pigtail to the trailer but the center pin which is normally used is always hot so I'm guessing abs.

Any idea where else this switch wiring may lead? Or tricks to find it?

 

Thanks, its definitely not at the pigtail. Tested the pigtail and every pin is as it should be with the center always hit for abs.

There is a dash light, will have to pull the dash and see if I can follow it