Check Engine Light on after Jump Start?

The other day stupid me jumped in my truck put the key in the ignition flipped it forward to acc so i could eject a cd from the radio. (hate you can just push eject) Got my cd out and in a hurry left the ignition on acc and went to work.:doh: well 8 hrs later I get home. Batteries dead. Obviously. So I had it jumped off... by a 7.3 powerstroke..:hehe: truck fired up no problem but the check engine light came on. Any ideas as to why? I should probly just check the code but I figured I'd ask here first... never know what answers might come back...

Thanks
Merica!
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