does anyone know how to fix check engine?

hi guys... i almost failed the smog check.. but the guy passed me anyways.... anyhow.. he says the check engine cannot be stayed on.... i got my car check at the dealer before.. they replaced the o2 sensors and the vavle... it still turns on... they ran it in the computer and says its because of that... and it still turns on... i dunno anymore.. driving me nuts.. any idea guys?? i got a 95 chrysler sebring 2.5l

thanks

streetlegalboi