Just purchased a used Keystone Cougar 5th-wheel RV and hooked it up to my 2018 GMC 3500 for the ride home. That's when I discovered that my truck does not recognize the trailer hook-up and thus, no trailer brakes! Does GMC use a different wiring pattern? Never had a problem with my older RV hooked up to the same truck. Any thoughts/ideas are greatly appreciated.
