Hello James,
I think it's a wiring problem, we had the same problem in the past. The wiring (several wires that are connected to each other) that runs to the OPSS had come loose, you can only see this if you loosen the protection. If I'm not mistaken, it was the wiring on the left side between the transmission and the engine. If I'm not mistaken, it was the wiring on the left side between the transmission and the engine. Our machine was a European version so I'm not sure if an American version has the same wiring.
Good luck
Marcb