Toyota Repair: Engine check, toyota corolla, trouble code

Question
My car is a 1988 toyota corolla Sr5, the "Engine check" in the instrument panel usually lights up. What particular part of the engine or system is it monitoring.  

Answer
Some time the check engine lights up due to minor things. for the example if the air cleaner is a bit dirty. The  light will be on. But if you want to find the exact fault then you have to diagnose your car for proper trouble code. with the  scanning tool.