Chevrolet: 2002 chevy prism check engine light, chevy prism, fan assy

Question
I see you work primarily with slightly older models but . . .
2002 chevy prism

Summer 2005
Fan assy replaced as it fell forward into the radiator. Radiator repaired as best as possible.

Sept 10th 2005
Check engine light (CEL) came on - need help.
I changed the oil - was low and needed changing but didn't fix the CEL
Going to try making sure the radiator is up to correct level.
Then the gas cap when I fill up the ol' gas tank today.
Other than that, I'm lost. I hear something called an oxygen sensor could be the culprit.
I looked it up and it looks like there may be 2 on my car, front and rear. I have no experience with cars. Is this something I can do without too much trouble? I am working with limited funds so any help you can give me will be appreciated. I am trying to learn more about my car - repair wise.

Thank you for your time.
Robin

Answer
Hi Robin, the check engine light tells you that there sensors are not working properly, it may be the oxygen sensor and yes it has two, but replacing them may cost you a lot of money for nothing. The best thing to do is take it to a shop and have it hooked to a analizer this will tell you what is wrong and save you money in the long run. when the CEL come on the computer stores a trouble code when its hooked up the mechanic can read the codes to tell him where the problem is. I hope this helps you if you need mmmore help just let me know. Regards, Keith.