1991 Ford Tempo service light

If you notice no change in drivability then it's probably just a minor fault like a sensor out of range? No major faults are detected like no oil pressure. You have red warning lights for major faults. You can get a code reader fairly cheaply if you must know what it is? Or have a shop read it for you. My grandaughter drove her tempo for 4 yrs and 100k with the check engine light on!