Before you spend money on an app sensor check the wiring. I've seen our faith share of pedals fail here too, but I've seen just as many where it was a wiring issue too.
Two key points from the diagnosis is resistance on the circuits and the possibility of a short between app1 circuit and app2 circuit.
Resistance value for the three circuits to each sensor (low reference, signal and 5v) should be no greater than 5 ohms. High resistance will change your value and if the difference is high enough between app1 and app2 this code sets. This can be a wiring issue or poor connection at either end. We've seen fretting corrosion on terminals (white crusty stuff) that will effect the values. Cleaning the terminals and some dielectric grease usually corrects the corrosion.
Checking for continuity between any of the circuits is the second item to look for. There should be none.
If the circuits have good resistance and no continuity to each other, then replace the pedal.