I just bought a 2018 Express 2500 Cargo van. The van came from U-Haul's fleet, it has no signs of ever having a 4-way plug on it, even though I could tell a hitch had been on the van. I want to install a 7-way with a brake controller for towing. After reading on the net, I found 4 factory wires under the brake pedal bundled and taped up with a GM tag indicating they are for a brake controller.. A red/white wire that is tagged BATT FU. A black wire tagged GND . A dark blue wire tagged TRL FD AUX CIR. A green/white wire tagged FU CHMSL. I checked them with a test light with key off, key on & engine running and none had power to them. Does any one know if these wires can be activated & used? If so how?

 

I found the same issue with my 2018 3500. I'm trying to figure out what's going on. Did you have any luck figuring out how to get power to the red & white wire?

 

I found my Chevrolet Express van trailer brake wiring from the factory underneath the driver side floor mat by the gas pedal if this helps