First things first- is the truck running? At the very least, it needs to be KOEO for power to be applied to the line side of the upfitter relay. I cannot say for certain but the engine may need to be running and not just key on.So I connected a light bar to the pass through wires and grounded light under the hood, connected pass through to upfitter switch and still now power to light. When I turn the switch on I am getting the amber light showing its on but getting nothing from the light.. Help Please!
Then check the fuse for the upfitter you are using.