Faulty EVAP vent valve (both sources). Open, short or high resistance in the vent valve control or power circuit (OBD-Codes.com). A blocked vent valve (OBD-Codes.com). Missing, loose or damaged gas cap (RepairPal). Torn or punctured EVAP hoses, a split carbon canister, a damaged filler neck or fuel tank, or a bad fuel tank sending-unit seal (RepairPal). A faulty PCM, which is rare (OBD-Codes.com).

Repair an open, short or high-resistance problem in the vent valve's control or power wiring. Replace a faulty or blocked vent valve. Reseat or replace the gas cap, or repair damaged hoses, canister or filler neck if testing finds a leak. Replace the PCM only after the valve and wiring check out (OBD-Codes.com).

P0446🌫 Emissions / EVAPUsually OK to drive

P0446: EVAP Vent Control Circuit Malfunction (Meaning, Causes, Fixes)

Q: What does P0446 mean?

P0446 points at the EVAP vent valve, the valve on the charcoal canister that lets fresh air in and seals the system for its leak test. Its wiring, the valve itself, or a failed leak test can set it. The EVAP system stores fuel vapor in a charcoal canister and later lets the engine draw it in and burn it. The vent valve on the canister lets fresh air into the system while vapor is purged, and closes to seal the system so the computer can run its leak test. OBD-Codes.com explains that the valve usually gets 12 volts with the key on, and the engine computer (ECM/PCM) closes it by grounding its control circuit. P0446 sets when the computer sees an open, a short to ground or a short to battery voltage on that circuit. The two sources frame the code a little differently. OBD-Codes.com treats it mainly as an electrical circuit fault, while RepairPal describes it as an improper voltage drop in the vent valve circuit, from too much or too little resistance, and says the PCM sets it when the EVAP system is venting when it shouldn't. Both also say some vehicles set P0446 when the system can't build or hold vacuum during the leak test: RepairPal says this applies to some PCMs on systems with a bypass valve, where a vent valve stuck closed, stuck open, a leak, or a bad fuel tank pressure sensor can all cause it.

Q: Can I keep driving with P0446?

Usually OK to drive. Usually safe to keep driving: OBD-Codes.com says there are no obvious symptoms beyond the check engine light. RepairPal rates it moderate, so get it diagnosed within a reasonable time, and sooner if you smell fuel.

Reviewed 2026-10-22 · Based on 2 cited source(s)

What P0446 means

The EVAP system stores fuel vapor in a charcoal canister and later lets the engine draw it in and burn it. The vent valve on the canister lets fresh air into the system while vapor is purged, and closes to seal the system so the computer can run its leak test. OBD-Codes.com explains that the valve usually gets 12 volts with the key on, and the engine computer (ECM/PCM) closes it by grounding its control circuit. P0446 sets when the computer sees an open, a short to ground or a short to battery voltage on that circuit. The two sources frame the code a little differently. OBD-Codes.com treats it mainly as an electrical circuit fault, while RepairPal describes it as an improper voltage drop in the vent valve circuit, from too much or too little resistance, and says the PCM sets it when the EVAP system is venting when it shouldn't. Both also say some vehicles set P0446 when the system can't build or hold vacuum during the leak test: RepairPal says this applies to some PCMs on systems with a bypass valve, where a vent valve stuck closed, stuck open, a leak, or a bad fuel tank pressure sensor can all cause it.

Severity: can I keep driving?

Usually OK to drive

Usually safe to keep driving: OBD-Codes.com says there are no obvious symptoms beyond the check engine light. RepairPal rates it moderate, so get it diagnosed within a reasonable time, and sooner if you smell fuel.

Common symptoms

Check engine light on
Usually nothing else the driver notices (both sources)
Sometimes a fuel smell from escaping fuel vapor (RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Faulty EVAP vent valve (both sources)
Open, short or high resistance in the vent valve control or power circuit (OBD-Codes.com)
A blocked vent valve (OBD-Codes.com)
Missing, loose or damaged gas cap (RepairPal)
Torn or punctured EVAP hoses, a split carbon canister, a damaged filler neck or fuel tank, or a bad fuel tank sending-unit seal (RepairPal)
A faulty PCM, which is rare (OBD-Codes.com)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Check that the gas cap is on, tight, and that its seal isn't dry or cracked (RepairPal lists the cap as a common cause and a common misdiagnosis).
Find the vent valve, usually on or near the charcoal canister by the fuel tank, and look for a loose or corroded connector and damaged wiring.
Look over the EVAP hoses you can reach for cuts or disconnected lines.

Typical fixes

Repair an open, short or high-resistance problem in the vent valve's control or power wiring
Replace a faulty or blocked vent valve
Reseat or replace the gas cap, or repair damaged hoses, canister or filler neck if testing finds a leak
Replace the PCM only after the valve and wiring check out (OBD-Codes.com)

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

Testing the vent valve's power and control circuits for opens, shorts and resistance, and commanding the valve with a scan tool to see if it operates.
Watching fuel tank pressure readings on a scan tool to confirm the fuel tank pressure sensor works, since the PCM relies on it for the leak test (RepairPal).
A close inspection, or smoke test, of the EVAP hoses, canister and filler neck for leaks.
RepairPal notes the fuel cap, purge valve and vent valve are all commonly misdiagnosed, so confirm the failed part by testing before replacing it.

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Will P0446 go away on its own?

RepairPal says most codes disappear once the onboard system no longer detects the issue. If the code keeps coming back, have the vent valve and its wiring diagnosed.

Is P0446 a leak code like P0455?

Not exactly. P0446 is mainly about the vent valve and its electrical circuit, while P0455 and P0442 are leak-size codes. But both sources note some vehicles also set P0446 when the system can't build or hold vacuum during the leak test, so a leak or bad gas cap can still be behind it.

Sources

Last reviewed 2026-10-22. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.