I've tested the horn relay and inputs, and everything works except for horn ground (power constant and ignition switch-conditional seem to be working appropriately, and I can jump the purple black to ground with key turned and horn will honk).
Where does the horn switch physically ground? Is it inside the steering wheel, or somewhere else?

Thank you!

 

if the horn is in the steering pad which makes contact with a steering shaft rod, the power to the pad switch is made by the mounting screws