2020 Yukon Tail Light Assembly partially working

tom3 said:

One of those pins would have power for the tailights, probably a connector back to the main wire, check for power on the trailer plug. Could be a fault at that connection point.

Click to expand...

Thanks, good idea! The light seems to have stopped after a recent towing trip too. i'll check there next.

I checked the trailer connector with a multimeter and the running lights blade registered voltage fine. No corrosion on both sides either.

I did notice that the each front side marker light is on the same fuse as the rear running light. The fuse is good and the side marker light is working.

I tried tracing the wire back, but on the ground there is not much room to work, so I don't see anything as far as I can trace it.

It looks like the passenger rear light assembly wiring harness runs across the frame and into another harness connector near the driver side rear axle. There seems to be a handful of connections feeding into this point. No visible damage there either.

I thought I would post my resolution in case anyone else runs into a similar issue.

I gave up troubleshooting, took the car to a local shop that has an employee who is an expert in vehicle electrical systems. The individual wire was diagnosed as having a break somewhere in the harness. I was told it was near impossible to trace back through the harness as it runs through many parts of the frame, the body, and other components between the fuse box and the tail light. Replacing the entire wiring harness would require separating the body and the frame, and would be very expensive and could run into other problems. While it was possible to tie the broken wire into another wire, I was told the best option would be to run a brand new wire from the fuse box back to the taillight harness, and spice it in, essentially replacing the one wire that was broken and keeping everything standard otherwise. This is what I did. It was about $400 total for the repair.