Check the plug on the back of the truck for corrosion. You may even have to open the plug up and check inside where the wires connect to the blades. When I would run the salt spreader in the winter it would cause this in the spring. Sometimes the corrosion was so bad I had to replace the whole plug.
Mike
2006 Chevy 2500 4X4 crew cab Gasser
2013 Dutchmen Denali 311 BHS (Love the trailer HATE the manufacture!)