P0449

P0449

Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

The Evaporative System (EVAP) prevents the fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system traps the fuel vapors and temporarily stores them in the charcoal canister. When the engine is running and other conditions allow, the fuel vapors are drawn by the engine vacuum from the EVAP charcoal canister and into the engine air intake. To balance the air pressure in the fuel tank, some air is allowed into the charcoal canister when needed.
The engine computer periodically runs the self-test to see if the Evaporative system is sealed tight. For the time of the test, the engine computer closes the vent valve. The trouble code P0449 means that the engine computer has detected a malfunction in the electric circuit that controls the vent valve/solenoid.
It could be a problem with the vent valve/solenoid itself or with the wiring that runs from the engine computer to the vent valve/solenoid. Sometimes the wires that run to the vent valve/solenoid get rubbed through or shorted. A bad connection at the vent valve/solenoid connector, a problem with the power supply or ground or an issue with the engine computer (ECM) itself can also cause the code P0449.
Typically the vent valve/solenoid is located somewhere closer to the fuel tank, not too far from the charcoal canister at the back of the vehicle. Many newer cars have the vent valve attached to the charcoal canister. The diagnostic procedure for the code P0449 usually involves operating the vent valve solenoid with a scan tool and testing the power supply voltage and the ground at the vent valve/solenoid, as well as checking its resistance.
Often a number of other EVAP system codes (e.g. P0452, P0455) could also be present, because if the vent valve/solenoid doesn’t work properly the whole EVAP system fails the self test.
The code P0449 is common in some GM trucks (e.g. Tahoe, Silverado, Suburban) and is often caused by a bad vent solenoid itself. The vent solenoid is an inexpensive part and is fairly easy to replace.

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