2001 gmc dually trailer brake light problem

[demi]

Hi folks,

I am trying to resolve a problem with my trailer brake light. All of the lights on the truck are functioning correctly. All of the lights on the trailer are functioning correctly except for the driver side brake light.

When I test the prong on the 7-round connector (for the driver side) I am not getting power when the brakes are applied. I do have power for the turn signal and park lights.

I have checked the fuses under hood and inside truck. I know that on 2003 and up trucks there is a module that switches between turn signals and brake lights. On my 2001 I do not have this module #10383321.

Does anyone know if or where there is a relay that controls the turn and brake lights.

Any help would be greatly appreciated, I am stumped or maybe I'm just missing something simple.

Thanks,
demi