P0446 EVAP Vent Control Fault
Drive normally - check soon
The EVAP vent valve, which lets fresh air in and out of the vapor system, is not doing what the computer commands. A blocked or failed vent valve is the usual cause. Harmless to drive, but it fails emissions tests.
- Safe to drive?
- Yes
- Typical cost at a shop
- $61-$643 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
- Carmaker bulletins
- 1 note with links
Read every EVAP code at once, clear them after the fix, and watch the EVAP monitor complete.
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What it means
The EVAP vent valve sits near the charcoal canister and lets air in and out of the vapor system. The computer closes it to run the leak test and opens it the rest of the time. P0446 means the vent valve or its control did not do what the computer asked.
The technical version
SAE defines P0446 as a vent control circuit fault, and carmakers set it for both electrical problems and a vent that does not open or close as commanded, judged from the tank pressure sensor. Dirt, water or spider webs in the vent line and filter, a failed solenoid, and wiring corrosion near the tank are the common causes.
Official name: Evaporative Emission Control System Vent Control Circuit Malfunction.
Symptoms
- The check engine light.
- The tank is hard to fill; the pump clicks off early.
- Sometimes a whoosh of air when you open the cap.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A failed or sticking vent valve | most common | It does not click or move when powered. |
| A blocked vent hose or vent filter (dirt, water, insects) | common | Debris in the vent line; worse after dirt roads or deep water. |
| Corroded wiring or a connector at the vent valve | common | Green corrosion at the connector near the tank. |
| A faulty tank pressure sensor | rare | Its reading does not change when the vent opens and closes. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Some cars let a scanner command the vent valve open and closed (a bidirectional test) and show EVAP vent status and fuel tank pressure. Tank pressure should change when the vent closes during purge. A vent that never changes state, or a tank pressure that stays fixed, points to the valve or its line.
What to check first, in order
-
Inspect the vent valve, its hose, filter and connector near the canister.
Blockage and corrosion are common.
What the data shows: No reading needed.
Cost: free to look
-
Read all EVAP codes and the vent status if your car shows it.
P0449 points to the circuit, P0446 alone to the valve or blockage.
What the data shows: Vent status should follow the command.
Cost: no cost if you have a scanner
-
Have the vent valve and wiring tested.
It separates a dead valve from a wiring fault.
What the data shows: Not a scanner step.
Cost: $61-$90 at a shop (Emission system diagnosis (shop), RepairPal)
-
Replace the vent valve, or the canister if the valve is part of it.
The usual fix.
What the data shows: EVAP readiness completes.
Cost: $558-$643 at a shop (EVAP canister replacement, RepairPal)
Is it safe to drive?
Drive normally - check soon
Yes. It is a fuel vapor fault, not a fuel leak.
Harmless to drive with. A stuck-closed vent can make the tank hard to fill (the pump keeps clicking off), and you will fail an emissions test until it is fixed.
Stop driving and get help if
- You see liquid fuel dripping or smell strong fuel inside the car.
What it costs
| Repair | Typical cost |
|---|---|
| Emission system diagnosis (shop)RepairPal, updated September 3, 2026 | $61-$90 |
| EVAP canister replacementRepairPal, updated September 3, 2026 | $558-$643 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner. RepairPal publishes no separate estimate for the EVAP vent valve; on some cars it mounts on the canister.
Can I clear it? Will it come back?
The EVAP test only runs under certain conditions, often a cold start after the car has sat for hours, with the tank between about a quarter and three quarters full. After the repair, clear the code and drive normally for several days. The EVAP monitor should show complete and the code should stay away.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
-
GM 2007-2010 Escalade, Avalanche, Suburban 1500, Tahoe, Yukon
GM bulletin 09-06-04-028D (April 2014) links P0442, P0446, P0455 and P0449 to water and corrosion at the EVAP vent (CVS) valve. A hard-to-fill tank is a sign.
GM 09-06-04-028D via NHTSA static.nhtsa.gov
Related codes
How Obie handles P0446
Obie reads the EVAP codes and readiness, tells you what to check first, and tracks whether the EVAP monitor completes on later drives. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Why is my gas tank hard to fill?
A blocked or stuck-closed vent valve can stop air leaving the tank, so the pump clicks off. P0446 often comes with it.
Can I drive with P0446?
Yes. It does not affect how the car runs, but it fails emissions tests.
What is the difference between P0446 and P0449?
P0449 points to the vent valve's electrical circuit. P0446 can also mean the valve or its line is blocked.
Sources
- RepairPal: P0446 code page repairpal.com
- RepairPal: Emission system diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: EVAP canister replacement (updated September 3, 2026) repairpal.com
- GM 09-06-04-028D via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0446 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.