only Marker rear lights not working

Only the rear marker lights are not working on the trailer. I hooked up to another trailer and the same issue, therefore im guessing its my truck. I changed out the relay and fuse and still having the issue. I cant expand the pins on the trailer to see if that helps because they are solid pins. Any help would be appreciated, thanks

All my lights on the truck work, all other lights on the trailer work.

 

I will definitely give it a try to replace the green pigtail. Thats the only thing i can think off that could be wrong.

 

I tried a different pigtail, same result. Just the market side lights and rear market lights won’t come on. Checked the socket as beat as I could, will try cleaning as best as possible when I deliver load. Could it be a ground fault and where can I look for a ground fault on the truck?? Thanks again in advance

 

2015 Freightliner cascadia 125 DD13

 

Agreed, as soon as i park the truck im going to test the socket on the truck. Take out the green pigtail off the truck and test the socket pins. Thats my guess as well, are the sickets pretty easy to replace, this will be a first for me on that one. I imagine a few screws and alot of pictures to make sure i return the wires correctly to the new socket. Hoping its just a lose wire on that socket.