check engine light stays on, won't pass smog help on 1994 Ford Explorer

check engine light has been on/off for the past 4 years. It was smogged in '10 even though ck.englt came on. It runs just fine. I am limited $$ and need to know what I should do first? I don't know that much about repair work. Please advise. Thanks 95945

Asked by for the 1994 Ford Explorer