I've not yet seen any type of circuit board that is used in conjunction with brake/turn signal/clearance lights on any type of trailer or motor home. Everything is wired directly from the plug to the harness of the trailer.
You should be able to clip the leads of a meter to each one of the pins in the 7 pin receptacle, apply the brakes, operate the turn signals or 4 way flashers and watch the needle/display on the meter move accordingly.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.