Durastar4300 range limited light on/ won’t move

I believe its "Range Inhibited" There are things that can be programmed into the
body module that can cause this if certain condition exist. Example if equipped
with a PTO and the PTO is engaged then the transmission could be Inhibited.
What is the truck used for?

 

Usually the transmission is not see a valid brake pressure switch command from the body controller. If your brake lights are stuck on, or never come on, diagnosing the brake switch is the first step. If you have hydraulic brakes, there is a 5 amp fuse that feeds the brake switch, make sure it isn't blown or has been knocked out of position. Air brakes have a different switch and they do go bad.