What causes a P0449 code?

P0449 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a P0449 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0449 active.

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

OBD-II

P0449

Evaporative Emission System Vent Control Circuit Malfunction

What it means

Indicates a mechanical or electrical failure within the EVAP canister vent valve circuit or the solenoid itself. Note: While common on gasoline engines, this code on a Class 8 vehicle usually indicates an incorrect ECM parameter setting or a specific auxiliary fuel system fault.