- Engine Light ON (or Service Engine Soon Warning Light)
- Possible a noticeable fuel odor caused by the release of fuel vapors

Dirt and dust intrusion into the EVAP canister vent hose assembly, resulting in restricted air flow, may cause this condition.

There is a bulletin for the following models:
1999-2007 Chevrolet Silverado (Classic) Models
2007-2008 Chevrolet Silverado Models

Chevrolet Factory Service Bulletin OBDII Code P0446

The P0446 codes triggered when an improper voltage signal is sent to Engine Control Module (ECM) through EVAP canister vent control valve.

The Evaporative System (EVAP) canister vent control valve is located on the EVAP canister and is used to seal the canister vent.

This solenoid valve responds to signals from the Engine Control Module (ECM). When the ECM sends an ON signal, the coil in the solenoid valve is energized. A plunger will then move to seal the canister vent. The ability to seal the vent is necessary for the on board diagnosis of other evaporative emission control system components.

This solenoid valve is used only for diagnosis, and usually remains opened.