first things first
serial number please?
secondly, is the battery charged fully? what state (condition) is the battery in? make sure its charged fully and all cells are in good condition.

Run a load test and check each cell and make sure you donot have any failing cells. Faulty cells can cause low voltage under a load and can cause random codes being triggered.

Check the cable tray where the cables go under the battery to the rear of the truck to the control panel. Any corrosion? Cables eaten up from acid corrosion?
Too many codes showing up

has this truck gotten wet (from rain or some other source such as pressure washing?)