I almost never blame the card, until every other possibility is exhausted. the fact you have these codes indicates for the -most- -part- that the card is working correctly.
if this truck can run at all under it's own power, then this seems to me, for all the world, like a bad connection, or possibly a bad contacts inside a switch, maybe the brake or directional switch or the Accel pot.
Are you ever able to get this truck to move under it's own power? You mentioned hitting a pot. perhaps you can mail me 'off list' for further tests, i would want to know what the voltages are on all the term board connections, with different switches activated (open and then closed)