Truck drive speed will only go up to creep to mid range. No code comes up on the display. Display shows all the mast swithes are working. Computer registars re-start and beep comes on. Display shows the pot is in the correct position and value. Also did a re-learn. The truck is equipped with wire guidance, drove the truck off the line to check sensor. Out side of the traction board, would anyone have any other suggesting ??