Yes a newbie at these. According to the Body Builders layout schematic the wires for the upfitter switches are "Located behind upfitter relay box".

I found the pass through wires on the driver side near parking brake exactly where everyone said. But my question is....are these pass through wires different than the actual wires that are "located behind the upfitter relay box". Or are these one in the same and where my hot connection needs to be made.

Sorry for the question. I have founds tons of info on this site in reference to them, just not this question that came to mind. Thanks!!
icee

 

The pass through wires are separate from the upfitter wires, there should be a plug for it if it's a newer vehicle (not sure below '11).

Check the doc below, should point you in the right direction (if your truck is 11+).

 

On my 2006 SD diesel the pigtails are located under the hood IIRC behind the master cylinder reservoir, all tied in a bundle.

 

The wires for the upfitter switches are different than the pass through wires. The upfitter wires are accessed by removing the relay box and fuse box located under the dash to the left of the steering column. Remove the trim panel, remove the fuse box and the wires are there. On my 05 anyway.

Brian

 

+1 ...this is your answer.

 

on my '08 the wires for the upfitters look similar to the passthough, but the stickers wrapped around them label them accordingly. They are in the same location as the PTO wires, just next to the steering column.