Check your forward and reverse contacts. The steer encoder will show a fault code when you key the truck on. It cuts out drive to left or right motors when turning, and it sounds like this is correct. So contacts, drive motor brushes , contacts have to also make contact when at rest. Also it will drive on only 1 motor working, check armature and brushes.

The Steering Encoder might be malfunctioning.

You might need to place a service call with the local Toyota dealer; I would expect their service department to have the correct diagnostic tool to be able to recalibrate the encoder.