John Deere 7920 w/Brown display and SF1 autoguide.  GPS wont work due to the tractor popping codes.  They all go back to the angle sensor and low voltage, da,da,da, angle sensor.  I've been on the phone w/ the JD dealer he can have a guy down tomorrow PM.  Is it something simple, he claims the angle sensor is on the front axle near the right knuckle, no such thing there I can see.   Hard to see the steering valve, but I have checked all connections I can find.  Do these sensors go bad or am I overlooking something??  Worked great the other day!  Any help appreciated.  Thanks

Codes are 523822.14    523822.05   522837.??