The most common thing is that the red on/off toggle switch is turned off when you are turning the truck on with the keyswitch or the keypad on the handle. I have had a few trucks get this code when trying to lift. It turned out the truck had one bad battery in the battery pack. If the truck has a battery pack with four 6 volt batteries in it you can test them one at a time with a volt meter. Leave them all connected and check the voltage right at the terminals one battery at a time while operating the lift or travel and see if the voltage drops way down. I have seen this more with the Champion/GNB sealed batteries but have also seen it with the non sealed ones. Good luck.