EVAP System Vent Control Circuit

What it means

The engine computer has detected a fault in controlling the vent valve, which opens the charcoal canister to outside air and closes it during the leak test. The fault may be electrical, and on some vehicles the code is also set when the system does not respond to the valve command because the vent is blocked.

Related codes: P0449P0447P0448P0455P0442

Symptoms4

• Check engine light on.
• Difficult refueling with the pump nozzle clicking off early if the valve stays closed.
• Occasional rush of air when opening the fuel cap.
• Usually no driving symptoms.

Possible causes5

• Failed or stuck vent valve.
• Vent opening or vent filter blocked by dust, dirt or insects.
• Corroded connector or damaged wiring, since the valve sits near the tank and is exposed to water and dust.
• Charcoal canister saturated with fuel from overfilling.
• Faulty tank pressure sensor giving a false reading.

How to diagnose5

1. Command the vent valve with a scan tool and listen for it to click.
2. Inspect the vent opening and filter for blockage.
3. Measure the valve coil resistance and check for supply voltage.
4. Inspect the wiring and connector near the tank for corrosion.
5. Watch tank pressure while opening and closing the valve with a scan tool.

How to fix5

1. Clean the vent opening or replace its filter.
2. Repair the corroded connector or wiring.
3. Replace the vent valve if it has failed.
4. Replace the charcoal canister if it is saturated, and avoid topping off after the nozzle clicks off.
5. Clear the codes and drive until the EVAP self-test completes.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low for cleaning the vent or repairing a connector, and rises when the vent valve or charcoal canister is replaced.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions