Mystery Wire

[SkyHighColorado]

The only real way to figure it out is to trace the wires. If that's the blue wire running with that red/orange wire in the loom, follow them all the way to the end and see where they go. If they run side by side to the end then follow the red wire under your dash and see if it's spliced into either a power source or tapped into the brake lights? I recently removed my trailer brake controller and it was wired completely different to this.

 

[BoxerPitMix]

Coming from the driver side firewall - it is the brake controller. The orange is your charge wire. I've these countless times when installing brake controllers.

Odd thing is, it ISN'T standard for any year. I've traced through harnesses on many different years of 400's that didn't have the wires for some reason and had to run them all the way back myself... Dunno why some have them, some don't. If they are there, they can be a real PITA to find. Sometimes you can look down on the firewall and see the blue & orange loops sticking out of the wire loom and just yank them out and hook them up... Sometimes they are buried farther down and you gotta dig for them.