Hi Ashley, How are things in the former homeland of my Mom?
Code 81 is the lift pot out of range. These 7400 's rarely have pot failures. The control handle cable is known to fall off or get loose. You can remove the handle by using a 5mm hex drive by the access hole under the handle, on top of the battery. the handle will come right out without taking any covers off. If the cable is ok, check the handle carefully for cracks. If it physically looks good and the pot is free to rotate, you can try RE-learn. You need access to the superword. Factory default is "2". But most likely someone changed it. Just hit the enter button while the truck is on and press 2 then enter. worth a try. If re-learn doesn't work then the pot may be faulty. You can change just the pot as it unplugs from the main card inside, or buy a rebuilt. Either way, you need superword to Re-learn the new pot. Soda pop or coffee is the only thing that ruins these pots. NB: this code can be generated by someone touching the lift as the Key is turned on. Good luck and please let me know how things turned out!