Is a sensor going bad?

A failing sensor will trip a "Check Engine" light. I wonder...could your thermocoupler have failed in an engaged position? OK - real people terms: It's possible that the free floating engine cooling fan is stuck "on" and what you are hearing is actually the fan roaring as you accelerate. Try this on an empty road: From a stop, pull the selector down into "1" and work up to a steady speed - shift to "2" - you should feel the truck shift gears and pick up more speed without having to give it more gas. the idea is to run the truck through the gears while ignoring the "noise". You should be able to feel it shift whenever you manually select the next gear and it should speed up without moving your right foot. Fan Clutch - Free Floating Fan - Thermocoupler - You should be able to hear the fan roar when you first start the truck for a minute or so and then it should quiet down until needed to cool off a warm engine. If it's stuck - it will roar all the time.

what did u find out because yours is doin the same thing mine is and its no fan mine is really not wanting to shift from second to drive