Check engine light came on...

[Alan06SUT]

Over the past couple of days, I have noticed some hard up shifts once the truck is good and warmed up. Today the check engine light came on while driving at about 80 on the highway. All vitials are fine, oil, temp, trans temp, etc. Nothing is leaking, and no other symptoms are noticable. I have driven it around some and the engine light still comes on each time I start it up and drive around. I will be taking it to the Stealership tomorrow but I wanted to get some possible ideas as to what it could be so I dont have to go back several times!!!

TIA.