P0446 code: EVAP vent control circuit

What P0446 means

P0446 is a generic SAE J2012 powertrain code: Evaporative Emission System Vent Control Circuit. The P means powertrain, the 0 means the definition is the same on every OBD2 vehicle, and the 4 places it in the auxiliary emissions group, where all the P044x EVAP codes live.

The vent valve (also called the canister vent solenoid) is usually mounted near the charcoal canister, often close to the fuel tank. It is normally open so air can flow in and out of the canister. During the EVAP self-test the computer closes it to seal the system. P0446 sets when the computer sees an electrical fault in the vent circuit or, on many vehicles, when the system does not respond as expected while the vent is commanded closed or open. How each manufacturer runs the test varies, so check the service information for your vehicle. Look up related EVAP codes in our code decoder.

Symptoms of P0446

P0446 rarely causes a drivability problem. The engine runs the same with or without a working vent valve. Signs you may notice:

• Check engine light on
• EVAP readiness monitor shows not ready, so the car can fail an emissions inspection
• Fuel pump nozzle clicking off early or the tank being hard to fill, if the vent is stuck closed or blocked
• Faint fuel smell near the rear of the car on some vehicles
• Other EVAP codes stored with it, such as P0455, P0442 or P0449

Common causes of P0446

Start with simple visual checks. Vent valves sit low on the vehicle where dirt, water and road salt reach them.

How to diagnose P0446

A scan tool with bidirectional controls saves time here, because you can command the vent valve open and closed and confirm it responds. See our guide to the best bidirectional scan tool if your current reader cannot do this.

1. 1

   Read all codes and save the freeze frame. Note other EVAP codes, since several together often point to a shared wiring or canister problem.

2. 2

   Check the gas cap is tight and the seal is in good shape, even though a cap problem more often sets P0455 or P0457.

3. 3

   Find the vent valve near the canister. Inspect the connector, wiring and vent hose for damage, dirt or insects.

4. 4

   Check the fuse that feeds the EVAP solenoids and confirm power at the vent valve connector with the key on.

5. 5

   Use the scan tool to command the vent valve closed and open. Listen and feel for a click. If your tool shows vent valve status or tank pressure in live data, watch for a change.

6. 6

   If the valve does not respond but has power and ground control, test it or replace it. Check for charcoal debris before fitting a new one.

7. 7

   Clear the code and drive normally. The EVAP monitor often needs specific conditions, such as a cold start and a fuel level between about a quarter and three quarters, to run. See readiness monitors explained.

How to fix it and can you drive with P0446?

Fix whatever the test points to: clear the blocked vent path, repair the wiring, or replace the valve. If you find charcoal in the vent line, replace the canister as well, or the new valve may clog again. Stop filling the tank after the pump nozzle clicks off; topping off is a common way canisters get damaged.

You can usually drive with P0446. It does not harm the engine and is not a safety issue in most cases. The downsides are a failed inspection and a check engine light that can hide a new, more serious fault. If you smell strong fuel vapor, have it checked promptly.

Note.Work on the EVAP system means working near fuel and fuel vapor. No smoking or sparks, work in a ventilated area, and support the vehicle on jack stands if you go underneath.

Related codes

Other EVAP codes you may see with P0446 include P0455 (large leak), P0456 (very small leak), P0442 (small leak), P0449 (vent valve or solenoid circuit) and P0496 (purge flow when not commanded). See all engine codes.

Frequently asked questions

Is P0446 serious? Usually not. It is an emissions fault, not an engine damage fault. It should still be fixed so your car can pass inspection and so the check engine light can warn you of new problems.

Can a loose gas cap cause P0446? A loose cap is more often tied to large leak codes like P0455. P0446 more commonly comes from the vent valve, its wiring or a blocked vent path, but checking the cap costs nothing.

Where is the EVAP vent valve? On many vehicles it sits on or near the charcoal canister, close to the fuel tank under the rear of the car. Location varies by make and model, so check the service information for yours.

Why did P0446 come back after I cleared it? The fault is still present. Clearing only resets the light; the computer sets the code again the next time the EVAP test runs and fails.