K.
Replacing your cap was a great start! Sometimes when check engine lights come on due to a code that your computer had tripped, they need to be reset and do not automatically go off. Most shops will scan your vehicle for free on their scanners and are a little more accurate that Auto Zone. (different type of dyno scanner) Any shop that will not scan your vehicle for free, do not use!!!! I personally am in the automotive industry and have been for 20 years combined. A lot of times, this can be a quick inexpensive fix, sometimes not, no guarantee. On the upside, in the state of IL, you have 3 opportunities to fix your emissions, but make sure the shop you take it to is an EPA certified shop. There is an amount of money to be spent, but after that amount, they will waive you for a year. IF you need any help, feel free to contact me. I know a lot of people at a lot of the shops in the northwest suburbs and also wholesale parts suppliers. (my hubby ran one for 13 years, and I currently run one and have worked in several area shops.)
Good luck to you! I know how stressful this can be!