EVAP Vent Solenoid
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Pontiac Grand Prix, 2003 Pontiac Bonneville, 2003 Chevrolet Monte Carlo, 2003 Chevrolet Impala, and 2003 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
The EVAP vent solenoid controls fresh airflow into the EVAP canister. The solenoid is normally open. The PCM will command the solenoid closed during some EVAP tests, allowing the system to be tested for leaks.