P0446 Code: Evaporative Emission System Vent Control Circuit

As you cruise down the road, enjoying the thrill of the open highway, suddenly, your check engine light flickers on, and you feel a pang of worry. You pull over and take a deep breath as you retrieve the diagnostic trouble code from your car’s computer: P0446. Your heart sinks as you read the description: “Evaporative Emission System Vent Control Circuit.” You know this is not something to be taken lightly.

What is a P0446 Code?

A P0446 code is generic for an evaporative emission system vent control circuit. The ECM detects a malfunction in the EVAP system and will set this code when there is an issue with one of its components, such as:

The fuel tank vent solenoid valve (FSV), which controls airflow from inside your fuel tank to outside of it.
The purge control valve (PCV) allows air into your intake manifold so that fuel vapors can be burned off more efficiently during engine operation.

If you have this trouble code stored in your vehicle’s computer, it means either one or both of these valves are not working correctly and must be fixed before further driving can occur safely.

Why do I have a P0446 Code?

The evaporative emission system is not working properly.
The vapor hose connecting the canister purge valve and fuel tank is disconnected or damaged.
The vapor hose connecting the canister purge valve and the fuel tank has been disconnected from its fitting on either of these components (canister purge valve or fuel tank).

Common Causes of a P0446 Code

A clogged fuel tank vent is the most common cause of a P0446 code. The evaporative emission control system relies on air flowing through the tank to help remove moisture from the gas and prevent corrosion. Any obstructions, such as dirt or debris in your vent line, can cause problems with your vehicle’s ability to pass its emissions test.

Another common reason for this code is a loose or damaged fuel cap; if you’ve recently bumped into something while driving or if your cap has become bent out of shape over time, it could be interfering with airflow into the fuel tank and causing moisture buildup in there instead of being vented outside as intended by design (which is what creates those harmless puffs of white smoke).

Symptoms of a P0446 Code

Check engine light is on.
Poor fuel mileage and increased fuel consumption.
Engine misfires, misfiring cylinders, or rough running due to the lack of proper ventilation of the EVAP canister (leak in hoses and connections between hoses and canister).

Conclusion