Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Saturn SC1 Check Engine Light Due to Gas Cap Issue
Saturn SC1 Problem
Average Mileage: 127,666 mi (117,000 mi - 140,000 mi)
Visitor, 2001 Saturn SC1, 117,000 mi
Check engine soon light came on. Mechanic checked the computer code and identified leaky gas cap. Going to replace cap.
Visitor, 2002 Saturn SC1, 126,000 mi
After just about every fill up, the light will come on. I re-seat the cap, light goes off within a few more starts.