Are you sure it's not the trailer? Check by plugging the trailer in question to another vehicle. If not possible than get a vehicle plug tester from your nearest auto parts store, shouldn't be more than $10-15, and test the connection on the truck. If tester fails, see post above by @Crash68My friend has a 2015 gas Ram 1500, when you connect the truck trailer plug to a trailer none of the lights come on. We have look at the trucks trailer plug but we can find any damage. PLEASE help if you can.