DTC code P0191 how to fix it?

I get a P0191 code when cold engine is first started and stays on until I clear it. If I clear the code when engine is warm it will stay off as long as the engine does not cool right down even if I stop and start it numerous times. But then when the engine has cooled right down the code comes back and stays until cleared again. The code can be cleared but returns until the engine warms up at which point it says off if cleared. This is a new body style truck.