Running lights or turn signals? If it's the running lights that aren't working then it's 100% the trailer since that's all one circuit on the truck.
When you get your truck back, The 7 pin has the wiring diagram on the cover. Use a multi meter and test your 7 pin.
99% of the time, it's the trailer not the truck.
When you get your truck back, The 7 pin has the wiring diagram on the cover. Use a multi meter and test your 7 pin.
99% of the time, it's the trailer not the truck.