Understanding the P0449 Chevy Trouble Code: Causes and Solutions

The Engine Control Module (ECM) has determined that a malfunction exists in the electrical circuit for the vent valve/solenoid in the evaporative emission control system.

The Evaporative Emission System is located on the (EVAP) canister vent control valve is located on the EVAP canister and is used to seal the canister vent. This solenoid (the EVAP canister vent control 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 onboard diagnosis of other evaporative emission control system components.
This solenoid valve is used only for diagnosis, and usually remains opened. When the vent is closed, under normal purge conditions, the evaporative emission control system is depressurized and allows EVAP Control System (Small Leak) diagnosis.

Car Trouble Symptoms
1. The Check Engine Warning Lights will be “ON”

Possible Cause of Problem
1. Purge Control Valve harness is open or shorted.
2. Purge Control Valve electrical circuit poor connection.
3. Faulty canister vent control valve.


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