# P0446: Evaporative Emission System Vent Control Circuit **Verdict:** Safe to drive Emissions - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $100-$500 - **Urgency:** Keep driving - **Most likely:** Stuck EVAP vent valve or clogged vent - **DIY?:** Steps 1-3 ## Quick answer P0446 means the engine computer has found a problem with the EVAP vent valve or the circuit that controls it. The vent valve lets fresh air into the charcoal canister and closes to seal the system during leak tests. A stuck vent valve, a clogged vent filter, or a wiring problem is the usual cause. ## What does P0446 mean? The EVAP vent valve, sometimes called the canister vent solenoid, sits on the fresh-air side of the charcoal canister, usually near the fuel tank. Most of the time it stays open so the canister can breathe: displaced air leaves through it while you refuel, and fresh air enters while the engine purges stored vapor. When the computer runs its leak test, it closes the vent valve to seal the system. Despite the word "circuit" in its official name, P0446 is used two ways depending on the maker. Some cars set it for an electrical problem in the vent valve control circuit. Many others set it when the vent does not perform as commanded, such as a valve that stays closed or a vent line that is blocked, which the computer sees as pressure or vacuum it did not expect. That is why a clogged vent filter can trigger this code. Most cars need the fault on two drive cycles before the check engine light comes on. ## What are the symptoms of P0446? - Check engine light on - Gas pump nozzle clicks off repeatedly while filling - Car drives normally - Failed emissions test ## What causes P0446? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Stuck or failed vent valve** (most common). The vent valve usually sits near the fuel tank or canister, where dirt, water, and road salt can make it stick. A valve stuck closed traps air in the tank, so the pump nozzle shuts off early and fueling becomes slow. A valve stuck open keeps the system from sealing for its leak test. 2. **Clogged vent filter or vent line** (common). The vent line and its filter pull fresh air from under the car, so mud, dust, spider webs, or insects can block them. When the canister cannot breathe, pressure builds while fueling and vacuum builds while purging. This is more common on trucks and SUVs driven on dirt roads or through deep puddles. 3. **Wiring or connector fault** (common). The vent valve wiring runs a long way under the car to the rear, where it is exposed to water, road salt, and debris. A corroded connector, a broken wire, or a loose pin can stop the valve from switching when the computer commands it. A resistance and voltage check at the connector usually finds it. 4. **Damaged charcoal canister** (less common). A charcoal canister that is cracked, packed with debris, or soaked with liquid fuel from repeated overfilling can restrict airflow through the vent side. Loose charcoal can also travel into the vent valve and jam it. If a new vent valve fails again quickly, the canister is a likely reason and should be checked. ## How do you diagnose P0446? 1. Inspect the vent valve, its connector, and the vent line under the car for damage or blockage. 2. Command the vent valve with a scan tool and listen for it to click. 3. Measure the valve's resistance and check for power and a control signal at the connector. 4. Blow through the vent line to make sure it is not clogged. ## How do you fix P0446, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Replace EVAP vent valve | $150-$400 | The most common fix. Some are sold only with the canister. | | Clean or replace vent filter and hose | $80-$250 | Fixes a blocked vent path. | | Repair vent valve wiring | $100-$300 | For corroded connectors or broken wires. | ## Is it safe to drive with P0446? > **Safe to drive.** It is safe to drive. If the tank becomes very hard to fill, have it fixed soon so you do not have to fuel slowly. ## Will P0446 fail an emissions test? P0446 with the check engine light on fails an OBD-based emissions test in most states. Because the vent valve has to close for every EVAP leak test, a vent problem can also keep the EVAP monitor from completing. Clearing the code before testing will leave that monitor not ready, so repair the vent first and allow several days of driving. ## After the repair: clearing P0446 After replacing the vent valve or clearing the vent line, clear the code and refuel once to confirm the pump nozzle no longer clicks off early. Then drive normally for several days, including an overnight cool-down with a partly full tank. The fix worked when the EVAP monitor shows ready and the code does not return. ## How to prevent P0446 - Stop fueling at the first click, since overfilling can push fuel and charcoal toward the vent valve. - Rinse mud and road salt from under the rear of the car, near the canister and vent valve. - Check the vent filter or vent line opening after off-road driving or driving through deep water. - Ask for the vent valve and its connector to be inspected whenever the car is on a lift. ## P0446 by make | Make | What to know | | --- | --- | | Chevrolet | Many Chevrolet and GMC trucks and SUVs set this code from a stuck vent solenoid mounted near the EVAP canister by the fuel tank, where it is exposed to road debris. | ## Codes often seen with P0446 - [P0449](/codes/p0449): Evaporative Emission System Vent Valve/Solenoid Circuit - [P0455](/codes/p0455): Evaporative Emission System Leak Detected (large leak) - [P0442](/codes/p0442): Evaporative Emission System Leak Detected (small leak) - [P0440](/codes/p0440): Evaporative Emission System ## Frequently asked questions ### Can I drive with a P0446 code? Yes, P0446 does not affect how the engine runs or harm it. It can make refueling slow because the tank cannot vent properly, and it will keep the check engine light on until fixed. Repair it before your next emissions test, and sooner if fueling becomes very difficult. ### Why does my gas pump keep clicking off? A stuck-closed vent valve or blocked vent line keeps air from leaving the tank while you fill, and that pressure trips the nozzle's automatic shutoff early. If it happens at every station and P0446 is stored, the vent system is the likely cause. A kinked filler vent hose can do the same thing. ### Where is the EVAP vent valve? On most vehicles the vent valve is near the fuel tank or the charcoal canister underneath the car, often toward the rear. On some vehicles it is mounted on the canister itself. Your service manual will show the exact location, and you may need to raise the car safely to reach it. ### How much does it cost to fix P0446? Most P0446 repairs cost $100 to $500 at an independent shop. A new vent valve usually runs $150 to $400, while clearing or replacing a blocked vent filter and hose costs about $80 to $250. Wiring repair is about $100 to $300, and some vent valves come only with the canister. ### Will P0446 make me fail an emissions test? Yes, P0446 will fail an OBD-based emissions test in most states while the check engine light is on. A faulty vent valve can also prevent the EVAP monitor from completing at all. Repair it, then drive for several days until the monitor is ready before you retest. ### Can I fix P0446 myself? You can often fix P0446 yourself if you can safely raise the car and reach the vent valve. Clearing a blocked vent line or replacing a bolt-on vent valve takes basic tools. Wiring faults and vent valves that are part of the canister assembly may be easier for a shop to handle. ### What is the difference between P0446 and P0449? Both codes involve the EVAP vent valve. P0446 can mean an electrical fault or a vent that is stuck or blocked, depending on the maker. P0449 points more directly at the electrical side of the vent valve or its wiring, so test the coil and connector first. ### Can a clogged vent filter cause P0446? Yes, a clogged vent filter or blocked vent line is a common cause of P0446 on many vehicles. The canister cannot breathe, so the computer sees pressure or vacuum it did not expect. Cleaning or replacing the filter and line can fix it without buying a new valve. ### Why does air rush out when I open my gas cap? A strong whoosh when you open the gas cap can mean the vent is blocked, so pressure or vacuum builds in the tank. A small hiss is normal on many cars because the system is sealed. A loud rush plus slow fueling and P0446 points to a stuck vent valve or clogged vent line. ### How do I test an EVAP vent valve? With the vent valve unplugged, most should let air pass freely, because they are normally open. Apply 12 volts briefly and it should click and block airflow. You can also measure coil resistance and command the valve closed with a scan tool while listening near the canister. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) ## Other emissions codes - [P0440 Evaporative Emission System](https://diagxcar.com/codes/p0440) - [P0441 Evaporative Emission System Incorrect Purge Flow](https://diagxcar.com/codes/p0441) - [P0442 Evaporative Emission System Leak Detected (small leak)](https://diagxcar.com/codes/p0442) - [P0443 Evaporative Emission System Purge Control Valve "A" Circuit](https://diagxcar.com/codes/p0443) - [P0449 Evaporative Emission System Vent Valve/Solenoid Circuit](https://diagxcar.com/codes/p0449) - [P0451 Evaporative Emission System Pressure Sensor/Switch "A" Circuit Range/Performance](https://diagxcar.com/codes/p0451) - [P0452 Evaporative Emission System Pressure Sensor/Switch "A" Circuit Low](https://diagxcar.com/codes/p0452) - [P0455 Evaporative Emission System Leak Detected (large leak)](https://diagxcar.com/codes/p0455) - [P0456 Evaporative Emission System Leak Detected (very small leak)](https://diagxcar.com/codes/p0456) - [P0457 Evaporative Emission System Leak Detected (fuel cap loose/off)](https://diagxcar.com/codes/p0457) - [P0498 Evaporative Emission System Vent Valve Control Circuit Low](https://diagxcar.com/codes/p0498) ## Symptoms - [Why does my car smell like gas?](https://diagxcar.com/symptoms/car-smells-like-gas) --- Source page: https://diagxcar.com/codes/p0446 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.