are you sure about the model number you posted? ERC060HGN?
verify that and give us a serial number too

but as brewski said they are possibly overheat codes
gaining access to diagnostics might tell you something, maybe but as he stated that 55555 is only a default passcode that comes from the factory, in alot of cases these days the servicing dealerships are instructed to change this to something else upon predelivery so it's a 50/50 chance that code will work.

If you're getting overheat codes i'd be looking at the battery and anything else that MAY cause a drag on the truck like the brake system. There may be something electroncially in the system setup if set wrong that may cause overheating but unlikely.
On some rare cases i've seen the wrong type tires cause some heatup issues because of the wrong durameter compound on the tire because it is not the right tire for the surface it is running on but as i said that is rare.
Check the battery and make sure it is the right one for this truck, make sure it is in good condition and charged up correctly, verify its charge level using a hydrometer and checking the SG in each cell.
In most cases i've ran into this issue it's usually been a battery problem of some sort. The fact that your getting an overheat code for the controller AND the motor at the same time tells me it's either the battery or something overloading the drive system enough to heat it up and trigger an overheat condition.