Silverado Trailer Lights - short between running and signals

[modernbeat]

I've got an issue with my truck trailer wiring that I can't find the cause of. I've isolated it to the truck, and not the trailer or the brake controller.

 

With the running lights off, the turn signals work correctly. With the running lights on, the running lights work until I hit the turn signals. Then the fuse for the trailer running lights pop. The turn signals still work. All the truck lights still work correctly.

 

Could this be an issue with the flasher module if the truck lights still work correctly? I suspect a damaged wiring harness, but the portion under the truck is undamaged.

 

Where should I look for a cause?

[modernbeat]

Guess I should have mentioned it's a very-very early 2003 Silverado 2500 2WD with the factory tow package, gas motor, automatic.

[markw8]

I would start by taking both the male and female ends apart and see if things look ok there.

 

Mark

[modernbeat]

Already did that, and replaced the last 12" length of the modular harness and the female terminal at the bumper.

[latreille89]

Check your ground wire, everytime ive had an issue with trailer lights, its been caused by a bad ground, corroded ground or something to that nature... Good luck