2019 Western Star 4700 Wiring Issue

Could be the end connector on the harness there that plugs into the back of the marker light might be bad. Same problem on my old freightliner, new connector fixed it.

 

Check the plug where it plugs in. May have a broken wire inside the plug itself.. Sometimes a wire comes out of the pin that go into the plug if whoever worked on it before didnt crimp the wire onto the pin good enough

 

Are the wires that run from the frame to the hood next to the hinges in good shape? They have a habit of rubbing through the wiring loom.

 

11 Function Digital Multimeter with Audible Continuity

Learning how to use a multimeter has helped me countless times with diagnosing and repairing electrical issues. It sounds like you have a good ground since the signals on those lights work. I'm guessing that problem is where both wires that supply voltage to those markers are linked together. Check the connection there and follow the wire back until you start getting voltage.

 

Yes check the plug they do come apart inside and will not let some or all lights work