P0447: EVAP Vent Control Circuit Open
P0447 means the engine computer found an open (broken or disconnected) electrical circuit to the EVAP vent valve, so the valve cannot be controlled and the system's leak test cannot run. It is a low-urgency fault that usually does not change how the car drives, but it turns on the check engine light and can keep the car from passing an emissions test.
You can keep driving
The fault does not normally affect driving and limp mode is not expected. The EVAP leak test cannot run while the code is set, so the car may fail an emissions inspection until it is fixed.
What it means
The EVAP (evaporative emission) system traps fuel vapor from the tank in a charcoal canister. A purge valve lets the engine draw that vapor off, and a vent valve opens the canister to fresh air. P0447 is the older code scheme for the vent valve circuit being open: P0446 is the general circuit fault and P0448 is a shorted circuit. It is used by Subaru (including the Saab 9-2X), VW and Nissan, while GM reports an open vent circuit as P0449 and Ford uses P0446. On Subaru, the valve gets power from the main relay and the engine module switches it to ground. If the module sees no voltage at its output, or the valve coil has high resistance (the normal range is 10-100 ohms), the code sets after two consecutive drives. The valve then stays in its rest position and the leak test cannot run.
Likely causes
- Vent valve connector corroded or disconnectedVery likely
The valve sits underneath the car where splash water and road dirt can corrode or loosen the connector.
- Vent valve coil openPossible
If the coil's resistance is outside the 10-100 ohm range, the valve circuit reads as open.
- Open wire to the module or open supply from the main relayPossible
A break in the wiring means the valve gets no power or cannot be switched to ground.
- Engine module or its connectorLess likely
A fault in the module's output or connector can look like an open circuit, but this is the least common cause.
What you may notice
- Check engine light on
- EVAP leak test does not run, so emissions readiness is not set
- Usually no change in how the car drives
What to check, cheapest first
- 1Read the code with a scan tool and note any related codes such as P0446, P0448 or P0449 before clearing anything. · you can do it
- 2Find the EVAP vent valve and inspect its connector for corrosion, water, bent pins or a loose fit. Reseat or clean it. · you can do it
- 3Inspect the visible wiring near the valve for damage, chafing or breaks. · you can do it
- 4Measure the vent valve coil resistance and compare it with the 10-100 ohm range. Replace the valve if it is outside that range. · mechanic
- 5Check for supply voltage from the main relay and for continuity of the wire to the engine module. · mechanic
- 6If the valve and wiring are good, test the module output and its connector. Then clear the code and complete the drive cycles to confirm the repair. · mechanic
Related codes
Frequently asked questions
Can I drive with a P0447 code?+
Yes. It usually causes no change in driving. Have it fixed so the check engine light goes off and the EVAP system can be tested.
Can a loose gas cap cause P0447?+
Not normally. P0447 is an electrical fault in the vent valve circuit, while a loose gas cap causes leak-type EVAP codes.
Will P0447 pass an emissions test?+
Probably not. The check engine light is on and the EVAP leak test cannot run, so the readiness status is not set.
How hard is the repair?+
It is rated easy and can be done at home in many cases. The estimated time is about 0.3 to 1.5 hours, depending on whether it is a connector, the valve or wiring.
Written with the help of AI from the public OBDex definition (CC0). Each make may use the code differently. Updated: 2026-11-10