Ford Repair: my 97 ford escort, emissions control, cable area

Question
So I need a test only smog check done this month but I was having a problem with my check engine light coming on. It first came on about 2 months ago so I gave it an oil change and tune up. Directly after my light went off but I believe this was only because the battery had been disconnected because about 75 miles later the light came back on. So I took it back to my boyfriends dad and he cleaned the battery cable area and disconnected it so it went off. Well it came back on again about 75 miles later so he checked the spark plugs. It went off and came back on again. So here I am frustrated to all hell because I know my car is not going to pass smog so I take it to get diagnosed yesterday. He says it was an emissions control reading. Can this be anything other than the cadillac converter or oxygen sensor? If not which is more likely to be going on? And what am I going to be looking at for repairs so I can get this car to pass smog? Thanks!

Since this I took my car into get a smog check and it passed.  But the next day my check engine light came back on.  What could be the problem?

Answer
there can be about 40 things turning the light on-some minor and some more serious no offense but unless your boyfriends dad is a mechanic and i am sure he is a nice guy but unless he is a mechanic with proper equipment you are going to stay frustrated because you haven't repaired anything taking battery cable off is just resetting the computer have a reputable garage check it out or find a boyfriend that is a mechanic i would just have it checked out.