Yes. Loose gas caps are one of the most common reasons the “CHECK ENGINE” light comes on. If CarMD tells you a loose gas cap is the culprit, tighten it until you hear it “click.” Then be patient. It may take a few trips around the block, or even a few separate starts, before the “CHECK ENGINE” light re-sets. If the cap remains loose, replace it. Make sure you use the correct cap for your specific make and model.View other possible causes of your check engine light and how to repair them here.