Check Engine Light On

Hi All,

I need some help with a car I plan to purchase. It is located at:
http://www1.getauto.com/autolinks_cardetail.html?x_dealer_id=AADTa&vinNum=1N4EB32A9NC727866

My dad and I looked at the car. It runs great, starts right up, great interior, looks like it had a good owner. Everything looked good, the only problem is that the check engine light is on. We think it might be something minor, but aren't sure what it could be. This is the only thing stopping it from passing smog. Any suggestions or ideas?

Thanks,
Robert