trailer wiring 04 tundra

My taillight on my trailer wiring has never worked. Carried to dealer before warranty went out they said it was working. Did not follow up and check behind them. Was not working. Anyway, I am fixing to pull a trailer on a trip and before I run a jumper wire from my taillights to my trailer harness, is their something in particular that I need to check on trailer towing package wiring? Maybe a quick fix?