DTC P0449: EVAP Vent Solenoid Valve Control Circuit: Description
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.
An ignition voltage is supplied directly to Evaporative (EVAP) emissions canister vent valve. Powertrain Control Module (PCM) controls EVAP vent valve by grounding control circuit via an internal switch called a driver. Primary function of driver is to supply ground for controlled component. PCM monitors status of driver. DTC sets when PCM detects an incorrect voltage for commanded state of driver.