Update, Monday Oct 30. Have been in Amarillo, Tx since thrus, the local GM dealer has been unable to accurately diagnose the issue with the truck trailer brake recognition issue. The trailer brake system has been ok'd. Local GM dealer has replaced front wheel sensor twice, once with aftermarket part, then GM part but does not fix problem. We are waiting now on a part, brake control electronic module, to come from GM whse in Dallas, due tues am and this will fix? Not a fun experience so far. Lots of money spent. There has to be a way these GM vehicles can more accurately diagnosed.