The truck is not running, when the swich is turned on the check engine light flashed fast, when a scanner is put on the truck a link error is showing. The truck was running fine and then started doing the above actions

 

What year truck is it? I would start by taking plugs off of the ecm and cleaning them with electrical cleaner. Check all of your ground wires and check your wiring making sur nothing it rubbed through or a mouse has chewed on them. Sounds like you have an open circuit somewhere