low & rough idle

First off i want to thank you guys for all the help i have been getting.. Only owned mine for a couple of months.. I need help again. My car idles to low . at the first line sbove zero on the tack. Very rough idle and sometimes dies. If i turn on my climate control, It idles great (perfect) at about the second mark or a little above.. It is smooth and steady if cli,ate control is on.. I didconnected the temp sensor. It made no diff. Now my check engine light is on all the time.. How do i get that off? Hope some one can give me an idea or two... Thanks again for the help.... Jim