Left turn and left brake lights not working

The problem was intermittent at first and now is permanent. I have checked the trailer connector for connectivity to the point where that is wired into the trailer wiring and it is OK. I have checked for voltage on the LED board and get tail lights OK (black wire) but no voltage for brake or turn (red wire). I checked the ohms to see if the red wire was grounded but it is not. I tried to find the wiring behind the license plate box but could not find it. I think I either have a broken wire somewhere between the trailer connector and the brake light. I have not found any place where I can get to the wires. I think my only solution is to run a new red wire from the front to the rear above the belly pan but am sure not looking forward to that.



Any suggestions would be welcome.