2002 Chevy Malibu - Small Leak in evap system

My check engine light came on and I had it diagnosed as a small leak in evap system. I was told it could be as simple as a bad gas cap so I had it replaced. The light still comes on, so I am not sure if there is a way to reset the sensor or if it is something more than the gas cap? You may have to take it to a shop that can test the EVAP system with a smoke machine. They can close off the vent solenoid with a high end scan tool or Tech2 and check for leaks in the system by using smoke and a bright halogen spot light to find the source of the leak.

An example:

In this picture the techs connected the smoke machine up to the evap system and filled the system full of pressurized smoke. They commanded the vent solenoid to close. The system becomes pressurized and the smoke will escape from any leaks in the system. In this case the vent solenoid was commanded closed, but the smoke was coming out of the vent solenoid because the solenoid wouldn't seal. You would never see that unless you used smoke.
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