It might be worth figuring out what the other code is that throws it into limp mode. The pressure switch won't do that on its own. The other code might give some insight into what is actually happening inside the transmission and what to do to fix it. It's possible it could be a bad solenoid pack.

 

The only code ive ever gotten was P0871, ill check again if it pops an engine light again, my code reader labels it as "Transmission Fluid Pressure Sensor/Switch "C" Circuit Range/Performance" for that code.