You must mean SC 5200 their no 4200 and a SC 4000 will only show a 3 digit code if you have the handset plugged into the controller.
If the steer tires are not in the straight position then the voltage to the motors will be different. (if your driving forks forward and turn right the right side motor volts drop and the left side stay the same this is to help it turn)
1 Dead battery.
2 Somebody has been playing with it and have F3.4 in features set wrong. (36 volt or 48 volt battery)
3 Go to A2.2.14 to ensure the battery volts are right for the battery 36 volt or 48 volt battery. 39 to 35 volts for a 36 volt battery, 52 to 45 volts for a 48 volt battery. if the reading from the battery to what the lift says is different (check battery volts with a volt meter at the battery connector) then go to Calibration C5 and set the volts the truck is reading to the volts the meter is reading at the connector.
4 replace access 2 (if you have more than one of the same trucks their then swap it over first from the other truck)
If you have a 4000 then one of the controllers are bad.
Your post is reading bad on the model number of the truck It shows it under a SC4000 but your post says SC 4200