2003 crewcab, below the 4wd shift **** and just to the left of the dash cubby there is a blank cover for a switch in my dash. Popped the cover out to put a switch there for something else and found a wire harness attached to it. Anyone have any idea what the harness is for?

 

On crewcabs that would be the wiring to install a passenger on/off air bag switch.

 

Correct. It was only offered in single cab and supercab trucks because you're supposed to disable airbags when you have skill children or a car seat in the front.

 

That blank cover is for the adjustable pedal switch.

 

Yep, airbag switch is on the other side of the radio/AC controls next to the power ports. Same deal on it, wiring is there whether or not the switch is.