Time to trade in the GM. If your vehicle lights work without trailer attached then the vehicle is fine. If they malfunction with the trailer attached, go back to whom gave you the trailer and ask for some Tylenol and explain you have a headache and are ready to inflict pain on them. Go to PA, get a wiring kit, read the instructions or have a competent person install it. In addition, run a dedicated WHITE ground wire from the trailer hitch end to each light socket.