Signal Lights...

International is infamous for electrical problems.

 

@Heavyd

 

Inside the 7-pin socket on the back side where the wires attach to the pins, I once had a screw holding a wire to a pin fall out and short two other pins.

 

Anything after 2004 have them.

You can get them reset at the dealer or better yet checked by the dealer. The used cost for them is about $600.

 

First, there are no cab light modules or cab control units on those. Only the smaller medium duty 4000,7000 in that date range have the body controllers. If everything on the truck works normally, but only the trailer is messed up, from what has been said, it is probably shorted inside the trailer socket at the back of the bunk. At those big connectors in your bunk, disconnect the one that has 2 orange and 1 brown wire. The brown wire is your marker light feed. 56C/56D orange is the left turn feed. 57C/57D orange is the right turn feed. If you only have your left turn on and then check for power at this connector and you only have flashing power at 56C or 56D and nothing else is flashing with it, then the wiring up to that point is ok. So if you have your trailer cord disconnected with the other connectors reconnected and all the pins in the socket have flashing power, then it is a bad socket.