The dreaded "Check Engine" light

[mccarrm]

I drove up the PCH this weekend starting from La Crescenta. Before starting, I decided it would be a good time to add a bottle of Techron.
I put 1 bottle to 12 gals of gas, as recommended.
After nearly depleteing the tank, I stopped and filled up. After one of our stops at a winery, the "Check Engine" light came on. I am not sure whether the above had anything to do with this, but its the only thing I've done recently.
Question: Is there anyway of accessing the problem code # and then get identifying it.