P0446 Code: EVAP Vent Valve Causes, Location and Fix

A P0446 code comes from the evaporative emission (EVAP) system, the sealed hoses, valves and charcoal canister that keep fuel vapor out of the air. A scan tool may print it as DTC P0446, and PO446 with a letter O is the same code.

The usual advice for any EVAP code is to check the gas cap first, and it costs nothing. But a loose cap sets a leak code, and P0446 is about the vent side.

What does a P0446 code mean?

P0446 means the vent valve didn't respond the way the computer expected. The vent valve sits on the fresh-air side of the charcoal canister: it stays open so the canister can breathe, and closes when the car seals the system to test it for leaks.

It's a generic OBD-II code, so it means the same on every make. It usually shows up when the car closes the valve for its own leak test and the system doesn't respond as expected.

Can you drive with a P0446 code?

Yes, unless one of the signs below shows up, because the vent valve doesn't fuel or run the engine. You may fail an emissions test, and a lit lamp can't warn you about the next fault, so plan the repair.

Four signs change that, because they point past the vent valve. We'd stop driving and get it checked if:

• You smell gasoline. Vapor or fuel is getting out, which is a fire risk. See why a car smells like gas.
• It stalls or won't start after refueling. That points beyond the vent valve. Ask for the purge valve and the other stored codes to be checked.
• The pump keeps clicking off and the tank won't fill. A blocked vent is behind GM's "hard to fill" bulletin. Don't keep topping off, and have it looked at before you can't fill the tank.
• Another warning comes on. A flashing check engine light or any other engine or temperature warning means more than this code.

What are the symptoms of a P0446 code?

You may see only the check engine light, because a vent valve doesn't feed the engine. The symptoms owners and carmakers do describe show up around the fuel tank:

• A tank that's hard to fill. The symptom GM names in the title of its bulletin for dust in the vent valve.
• A failed emissions check. The stored code alone can fail an inspection in states that read the computer.
• A hard start after refueling. In 1 of the 4 federal complaints, alongside another code. It points to the purge side, so see Safety.

None of these names the failed part. The other stored codes, the weather when it set and a valve test narrow it down, which is where the fix steps below start.

Where is the EVAP vent valve located?

On or near the charcoal canister: on several GM SUVs and crossovers it joins the canister body with an O-ring. GM calls it the canister vent solenoid. On its older full-size trucks the valve breathes through a vent line that runs up to a filter at the fuel filler.

Where the canister itself sits varies by model, so the exact spot on your car is in its service manual or with the shop. That location matters: dust, water and road splash reach the fresh-air side, which is why the carmakers' fixes are about what gets into it.

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What causes a P0446 code?

Anything that stops the vent valve opening, closing or breathing: something blocking its fresh-air side, water or ice, or a failed valve or seal. Most of GM's bulletins for the code are about what gets into the valve.

P0446 alone confirms none of them, because the code says the valve didn't respond, not why. Each cause below comes with its test.

1. Dust, dirt and spider webs

The vent valve breathes through a fresh-air inlet, and anything that plugs it stops the valve working the way the computer expects. GM has filed several fixes for dust and for spiders nesting in the canister's fresh-air port, on trucks, cars and small SUVs.

The fixes are a sealed vent valve, an in-line filter or a cleaned and replaced canister. On its newest pickups GM calls the dust filter a customer-pay alteration, an add-on the owner pays for even under warranty.

2. Water and ice

Water that gets into the vent line can freeze and block it. Ice on the fuel tank pressure sensor, which reads pressure in the sealed system, can also set P0446 with nothing wrong with the valve. GM has bulletins for both, water trapped in the canister filter pipe and ice on that sensor.

For ice on the sensor, GM's instruction is to dry the area and replace nothing. A P0446 that sets in freezing weather may need drying, not a new part, so mention the weather when you book the car in.

3. The vent valve and its seal

The valve itself can stick or fail, and the O-ring where it joins the canister can leak. Either way the system won't seal for its test, so the vent check fails even when the wiring is fine.

GM has a bulletin for the O-ring leak on several of its SUVs and crossovers. GM also tells technicians not to replace the canister unless it fails the leak test or has taken in too much dirt, dust or water, so ask what the test showed before paying for a canister.

A clogged vent filter

How do you fix a P0446 code?

Look before you buy, because several of the carmakers' fixes need no new part. To fix a P0446 code, work through the 5 steps below, in order, and the first three cost little or nothing:

1. Read and save every code. Write down P0446 and anything beside it. P0449 adds the wiring to the checks, and a leak code points at the seal or the canister.
2. Run the VIN. A dealer checks bulletins by VIN, the 17-character vehicle identification number, and our free VIN checker lists the recall campaigns for your car's model year.
3. Note the weather and look at the fresh-air side. Tell the shop if it set in freezing weather, and ask it to check the vent valve's inlet and connector for dust, webs, water or corrosion.
4. Ask for a vent valve test. A shop can command the valve open and shut with a scan tool and check it seals, and check the O-ring where it meets the canister.
5. Replace only what the test found. Clear the code after the repair and drive normally until the EVAP self-test, the monitor, reads ready again.

If the dealer's VIN check finds no bulletin, the valve test still decides. Checking the cap costs nothing, but a new one isn't on this list on purpose: a loose cap sets a leak code, and this one is about a valve.

How much does it cost to fix a P0446 code?

Sometimes nothing for parts. On GM's 2023–2026 midsize pickups, a code set in freezing weather needs drying, not a part, so run the VIN first. GM's other bulletins fit a sealed vent valve, add an in-line filter or replace the canister.

Where a part is needed, a new evaporative canister filter pipe on a 2016–2019 Cruze 1.4L, under GM bulletin 17-NA-233 of November 2019, costs about $50–$65 at an independent shop, parts and labor, on GM's 0.6 hours. A vent valve or a canister costs more.

So ask for the test result, the hours and the rate on the written quote. Ask too whether the diagnosis fee comes off if you approve the repair.

Will a P0446 code fail an emissions test and can you reset it?

It can, in states that read the car's computer, and clearing it first doesn't help. A lit check engine light fails there.

Erasing the code leaves the evaporative monitor, the car's own self-test of the EVAP system, reading "not ready". That may also be rejected, depending on the state and the car's model year.

Only driving sets the monitor back to ready, because the check runs by itself when its conditions are met. Ask the shop how much driving your car needs after the repair before you go back for the test.

What's the difference between P0446 and P0449?

P0446 says the vent valve didn't do what it was told, and P0449 says its electrical circuit has a fault. With both stored, have the connector and wiring checked for corrosion as well as the fresh-air side, because GM lists P0449 with P0446 for dust and a leaking O-ring.

Other codes beside P0446 point somewhere else. Each has its own guide:

• P0455 or P0442. A leak code as well. GM's dust and O-ring bulletins list these with P0446. See P0455 and P0442.
• P0441. The purge side of the same system. See P0441.
• P0443. The purge valve's own circuit. See P0443.

Is P0446 common on a Chevy?

In the paperwork, yes. Nearly all the carmaker bulletins since 2010 that name it are GM's, and the rest come from Isuzu and Volvo.

The owner complaints don't show it: P0446 appears in only 4 federal complaints from the 2010–2025 model years, and none of them says a part was replaced. Almost nobody files a complaint about a vent valve, so read the bulletins, not the complaint count.

Common questions

Asked most often

What is the most common cause of the P0446 code?

Dust, dirt or spider webs blocking the vent valve's fresh-air side, in most of GM's bulletins, then water and ice. The other cause is a failed vent valve or a leaking O-ring where it joins the canister.

How do I reset a P0446 code?

Fix the cause first: a scan tool can erase the code, but that leaves the evaporative monitor reading "not ready", and only driving sets it back. Ask the shop how much driving your car needs after the repair before you go back for an emissions test.

What is the most probable cause for a P0446 on a Chevy Silverado?

GM's bulletins for its full-size trucks blame dust and dirt in the canister vent valve. The fix is a sealed valve on older trucks and an in-line filter, paid by the owner, on newer ones.

Will a new gas cap fix P0446?

Almost certainly not, because a loose cap sets a leak code such as P0455, P0442 or P0456. Check the cap because it's free, but P0446 is about the vent valve.

Prices are ranges compiled in November 2026 for the US market and vary by region, engine and shop rate. Prices from $10 up are rounded to the nearest dollar, and the totals in the cost box to the nearest $10. Below $10 they're exact. This article is general information, not advice about your specific vehicle. See the disclaimer.