Check Engine

I have a galant '92 MPI automatic. The check engine indicator in the dashboard keeps lighting up! It first lighted when we found out the transmission had a problem. The transmission has no problems anymore coz it has been repaired. It lighted again then the mechanic found out there was too much fluid into the transmission so he drained it then the check engine was gone. Now, 5 days later, it lighted again! But I don't feel anything wrong with the car. I'm thinking of pushing the car over the cliff now! Please help if anyone knows something about this car.