You sure that's not a PE 4000 all 4500 codes are 3 numbers. If its a 4000 then the throttle wiper input fault. Check the voltage at pin 16 at the controller CA404 leave the handle up the voltage should be about 4.4 and then turn the handle (twist grip) it should smoothly go to about 0.2 in each direction. Adjust the pot as needed or replace. If your not getting voltage it's usually a broke wire in the handle harness where it bends when the handle is lowered.
If this is a 4500 then the display should not be showing a 2 number code always 3 numbers. If you power the truck up and the display goes out then take a hammer and tap on the lift pump solenoid this is usually a stuck solenoid. Then rekey it if that works then replace it.
Report back with where your actually getting this code from.