You may want to wait to see if someone posts with experience with this issue or cautions. This area can cause ouchies or death. Disconnect battery and research safety steps.
You can let the magic smoke out of the electrical components that run your truck by shorting, bending or breaking wires, or with many other actions. Magic smoke can make fire. Proceed with care.
Look at the top first, look for signs of rust, corrosion, or water near the fuses and relays. You could pull the trailer light fuses at this point if you wanted. If that works the wiring issue could be this unit, the connections to it on the bottom, or somewhere in the wiring harness to the trailer connector. You can visually inspect the harnesses from the back of the truck forward.
If your brave there are four clips to unhook so you can look at the bottom to let you examine the connectors and cables at then bottom. In addition to signs of rust, corrosion, or water you can look for loose wires or connectors.
Random youtube video of guy replacing the entire thing that may help visualize how things connect to it -
