What is the difference between P0446 and P0449?

P0446 is often a malfunction signal during the EVAP test. P0449 is more specifically a circuit performance issue with the vent solenoid. In practice, the diagnosis and fix are very similar.

Why is this so common on GM trucks?

The vent solenoid on many GM trucks sits underneath near the fuel tank, where it is exposed to road salt and moisture. The connector corrodes faster than the solenoid itself fails.

Can I pass emissions with P0449?

No. Any active EVAP code will cause an automatic failure in states that test OBD readiness.

Codes › P0449

P0449: The EVAP vent solenoid circuit is not working

Evaporative Emission Control System Vent Valve/Solenoid Circuit Malfunction

Low severityCan you keep driving?

Yes. This is purely an EVAP emissions fault. The car drives normally. Fix it before your next emissions test.

What it means

P0449 is closely related to P0446. Both involve the EVAP vent valve circuit. The distinction is that P0449 focuses on the electrical circuit performance of the vent solenoid, not a specific open or short. The vent solenoid controls fresh air entry into the charcoal canister. If the computer cannot verify that the solenoid is operating correctly, it stores this code. On many GM vehicles, this code is extremely common and is often caused by a corroded connector at the vent valve rather than a failed solenoid.

Common causes

Corroded or damaged connector at the vent solenoidVery common on GM trucks and SUVs, especially in regions with road salt.
Failed vent solenoidInternal coil failure causes an open circuit that the PCM detects.
Broken wire in the harness near the solenoidThe solenoid is near the fuel tank and exposed to undercarriage conditions.
PCM faultExtremely rare. Only consider this after ruling out the solenoid and wiring.

What it costs

Vent solenoid replacement$50 to $180
Connector repair or pigtail$30 to $120

Symptoms

Check engine light on
No driving symptoms
Possible faint fuel smell
Failed emissions test

What to do next

On GM vehicles especially, start by cleaning and inspecting the vent solenoid connector before buying any parts. Road salt and moisture corrode these connectors quickly. If cleaning the connector does not fix it, test the solenoid resistance and replace it if out of spec.

Lewis captures the EVAP system self-test results from the vehicle's monitors so you can see exactly when the fault was detected in the test cycle. Download Lewis.

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FAQ

What is the difference between P0446 and P0449?: P0446 is often a malfunction signal during the EVAP test. P0449 is more specifically a circuit performance issue with the vent solenoid. In practice, the diagnosis and fix are very similar.
Why is this so common on GM trucks?: The vent solenoid on many GM trucks sits underneath near the fuel tank, where it is exposed to road salt and moisture. The connector corrodes faster than the solenoid itself fails.
Can I pass emissions with P0449?: No. Any active EVAP code will cause an automatic failure in states that test OBD readiness.