P0446 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P0446 – Evaporative Emission Control System Vent Control Circuit Malfunction


P0446: DIY Repairing Video Tutorial


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P0446: What does it mean?

The Codes P0446 indicates a malfunction of the Evaporative Emission Control System(EVAP) Vent Control Circuit.

The EVAP is designed to prevent excessive fuel vapor from escaping into the atmosphere by absorbing them into charcoal pellets. There are two important valves that control when air can flow in and out of the system: 

  • The vent control valve lets air into the charcoal canister
  • The purge control valve lets vapors out of the EVAP and into the engine air intake.

Both valves are controlled by the Engine Control Module(ECM) and it periodically tests the valves for leaks. Any problems during these periodic tests will send the trouble code P0446.

Severity: Low

Not important, as you usually will not notice any malfunctions other than a lit check engine light. But it should be addressed as you cannot pass the emission test with it present.

Difficulty of diagnosis or repair: 2 out of 5

P0446 Possible Symptoms

P0456 will not always show itself except the engine light/service engine soon warning light on. Sometimes, you may notice a small fuel odor caused by the problem.

  • Engine Light ON (or Service Engine Soon Warning Light)
  • Possible a noticeable fuel odor caused by the release of fuel vapors

P0446: Possible Causes

There are many possible causes for the code P0446, including:

  • Missing Fuel cap
  • Incorrect fuel filler cap used
  • Fuel filler cap remains open or fails to close
  • Foreign matter caught in the fuel filler cap
  • Vent control valve harness is open or shorted
  • Vent control valve circuit poor electrical connection
  • Faulty vent control valve

Possible Checks/Fixes you can do yourself:

When you see a DTC Code P0446, there’re several checks you can do:

  1. Check the code from your OBD2 Scanner / Car Code Scanner and verify that it’s the only code present. If other codes are on the list, they should be checked first.
  2. If you have other codes such as P0441or P0440, the issue might be a solenoid failure or a more complex system leak. Address these issues first.
  3. If Code P0446 is the only code present, check your gas cap to see if it’s open or loose. Tighten your gas cap and the code might be cleared. 
  4. After you tighten the gas cap, the engine light may turn off after several drive cycles. It will be completed mostly after a normal day drive.
  5. If the engine light doesn’t go off, inspect your gas cap for physical damage or deterioration. It’s not always noticeable, you can try to replace your gas cap as it’s not expensive. It usually will clear the codes P0446.
  6. If the fuel cap didn’t fix it, you can check for aged, cracked or disconnected hoses of the EVAP near or connected to the engine air box. This is a common problem for old cars because of aged rubber hoses and dry-out gaskets. Replace the hoses and clear the code.
  7. If a replaced hose doesn’t solve the problem and the code comes back again, visually inspect the charcoal canister for leaks and other damages. Replace it if necessary.
  8. If all fixes above don’t solve the problem, you should consider performing an EVAP system check. You can do it in most repair shops and car dealers. They will usually perform a smoke check through your EVAP and the smoke will show if there’s any leak from any hoses or seals. 

How much is the cost to clear P0446?

For car code P0446, several repairs may apply, and the cost estimations are below:

  • Replace the Gas Cap: $20-$60
  • EVAP Line: $20-$100
  • EVAP Vent Control Valve: $150-$200
  • Replace the charcoal canister: $70
  • Charcoal Canister Vent Control Valve $150-$200