check engine light

need some input on this please, I have a 2010 DC, check engine light came on a few days ago, it was the day after I refueled truck. I figured maybe I didn't close gas cap all the way so I took cap off and put back on the re-set the CEL by disconnecting battery. The CEL has not come back on but my fuel economy is horrible, is there any way to figure out what code was if the CEL is not on, will the light come back on?? Any ideas

 

You cleared it, gonna have to wait until it pops up again. How many tanks of fuel are you basing you fuel consumption on?

 

same tank. Im right at the half way mark and the difference is about 45-50 miles. It don't seem to be running any different but the mileage is way off of norm.