not all ep20kt have the same error codes, a serial number will be needed to insure the correct code information.
but it is my guess that your code refers to the right drive motor "faulty field" or a faulty h bridge board, faulty logic card or faulty controller harness.
unless you are very familiar with the controller in this unit, I would suggest that the local cat dealer may well be the best choice of repair, as this is not a trivial truck to troubleshoot, and kinda high dollar to throw parts at.