ABS Trailer Brake Idiot Light... 2008 ProStar

[Waterloo]

I have had the trailer checked, along with the pigtail... Problem is in the tractor, had two shops check the trailer. And we all know about the compass module. I touch the brakes, ABS Trailer light on dash lights up. I replaced all of the fuses, is there a relay somewhere I do not know about, or a wiring fix? I read somewhere about these ABS systems and the wireing at the back of the cab where the pigtail plugs in but cannot find the website I read about this issue. The trailer I pull is a 2011 and in very good condition. Any help appreciated.