First off any codes? Lost of other items can cause erratic operations. Such as running to cold or temp sensor issues. If no codes I would drive it and monitor the sensors with a scan tool. If there is codes fix them and go from there.
Going to check for codes either today or tomorrow, however, as you may have seen in another post of mine I'd been having an issue with it building nearly zero heat, had a stuck open t stat, it's now fixed and has good heat again but havent been out with the truck yet, but that's interesting, didnt realize that could affect things in that way. I'll update when I know something for sure. Thanks for the info!
