What l know this is and older reach if you are standing on the truck by your right leg there is a cover with l think two Allen screws remove the screws and take the cover off in there will be the start contractor and fuses at the bottom is the drive controller might be curtis controller the best way to pull codes is with a hand set connected to the box if not l believe there is a small green light that will blink if there is a fault also that controller only controls the drive circuit if you pull off the top cover where the joy stick is on the right side there is another controller called the nib. board that controls the hyd and also the handle for forward and reverse there will numbers on the board as to what hyd you are working and all switches as far as brake and operater petal if a problem a different number will appear then you can look up number to track down problem. as far as what you are dealing with l believe it is with the drive circuit some codes are just warning codes l think a yellow light will come on for a second on dash. with out hand set you can not see history codes. if hard fault count blinks and look for code.