How do you erase check engine light on 2002 buich century. guy at filling station didnt turn cap enough.

What is the trouble code the vehicle is displaying? The check engine light comes on for several different reasons. One reason is when the vehicle reaches a certain milage the light comes on automatically so you have to take the vehicle to the dealer for service, usually around every 50,000 miles so the smog emission system can be checked to make sure it is working correctly. The other is if the vehicle is equiped with an ECM (Engine Control Module) and it detects a problem with the engine operations. Your local dealer can put the vehicle on a computer to diaginose the problem and/or trouble code. The check engine light is usually reset by the dealer with the computer after the problem is corrected. One thing to be aware of is that some repair facilities cut the wire for the lamp to make it go off so you won't see it because they don't have the equipment to reset it. To check for this turn on the ignition to the run position and check to see that all the warning lights are on and displaying before starting the car. The check engine should light also signfying it is working correctly. Good Luck, RAC

It should go out in a few days if that's really why it's on. Make sure you've tightened the cap