My 2000 Buick Century while idling in park or at a traffic light idles rough. Sounds like it hesitates

With warning lights always on -- there are concerns always present. They are not likely to be erroneous in nature. I think there are likely multiple serious issues with your Century, and it will take some time and patience and the skill of an experienced technician properly equipped to perform testing. There isn't a quick idea or two to relate -- there are dozens of possibilities here that need to be checked into. Pulling a code is merely a single, initial action to get some clues, but won't answer your questions. I'm sorry to say - seek guidance locally - check the link below to find a local shop near you to help. www.repairpal.com/repair-shops