I'd start checking for shorted wires in the axle tubes. If the SC indication is there all the time, a simple resistance measurement with an ohm meter from the brake power pin of the 7-pin to ground will show the fault. If the SC indication is intermittent, you might not see the short when you are not bounding down the road. My TV kept reporting errors like "trailer disconnected" and "wiring problem". After a lot of troubleshooting, I bypassed the wires inside the axle tubes and the problem went away. When I pulled the wires out of the axle tubes, they were chaffed through to the conductors in several places.
2012 3150RL. G614 tires. Hardwired surge protector. Level-Up Hydraulic leveling.
2013 F-350 Lariat 6.7 PSD SRW SC LB 4X4 OEM hitch, air self-leveling on rear. 57-gallon replacement fuel tank. DieselSite water separator/fuel filter.