What if the check engine light doesnt turn on? I had a smog check. it didnt pass

poss bad bulb and take it to a mech that can diag all codes and repair

What it sounds like is that your "Check Engine" Light is not coming on because the bulb burned out or someone took it out. With it not working you did not know that you were driving around with vehicle problems. The codes represent different systems in the vehicle and need to be properly diagnosed and repaired as well as the light fixed in order to pass smog. The prevous shop above is correct....it will need to go to a repair facility that has the equipment to properly diagnose & repair your vehicle.