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!