why is the check engine light on after replacing the battery?

Where would I check the code ?

take it to Autozone.they will read the code/codes for the check engine light.ask them to print the code/codes out for you,it's free.then post codes here.

Ok I went. This is the code P0603 Internal control module keep alive memory Malfunction

clean all the connections to the battery,grounds.clean very well.make them all real shiny,like new.check all of them very good and clean them up.