P0446 – Meaning, Causes, Symptoms, & Fixes
Code P0446 Definition
Evaporative Emission Control System Vent Control Circuit Malfunction
What Does P0446 Mean?
The evaporative emission control (EVAP) system prevents fuel vapors from escaping into the atmosphere. The fuel vapors from the fuel tank are absorbed and stored by charcoal pellets in the charcoal canister. The vent control valve is controlled by the engine control module (ECM) and allows air to flow into the charcoal canister to purge the gas vapors into the engine air intake to be burned. The flow of the gas vapors from the charcoal canister to the engine air intake is controlled by a purge valve. The vent control valve is normally opened when the engine is on, and the purge volume control valve is normally closed and is controlled by the ECM to open when it is ready to purge the stored fuel vapors from the charcoal canister. However, the ECM occasionally performs leak tests to ensure the evaporative emission control system is working properly when the vehicle is turned off. During the leak test, the ECM closes the vent control valve to create a sealed EVAP system. When P0446 is triggered, the ECM has detected a short in the circuitry to activate the vent control valve, or the EVAP system failed to maintain the proper pressure during the active EVAP leak test.
What Are The Symptoms Of P0446?
- Check Engine Light is on
- A slight decrease in fuel economy
- Gasoline smell
What Is The Cause Of P0446?
- Missing, defective, damaged, or loose gas cap (most common)
- Defective EVAP Canister Vent Control Valve
- Distorted, damaged or cracked Fuel Tank Filler Neck
- Torn or punctured Evaporative system hose(s)
- Defective Fuel Tank Sending Unit gasket or seal
- Split or damaged Carbon Canister
- Defective or damaged fuel tank
- Open or shorted electrical connections
How Serious is Code P0446? – Low
The driver will likely not notice any symptoms associated with P0446 other than the check engine light being on. However, as with all check engine light diagnostic trouble codes, you should repair it as soon as possible to return the vehicle to normal operation.
Tools Needed to Diagnosis Code P0496
How To Diagnose And Repair Code P0446:
Difficulty of Diagnosis and Repair – 2 out of 5
- Scan your vehicle to verify P0446 is the only code present. If other codes are present regarding fuel pressure or the fuel system, repair and diagnose those first. If it is paired with P0441, P0440, and/or P0446 there is most likely a solenoid failure, leaking charcoal canister, or a more complex EVAP leak.
- Inspect your gas cap to see if it is loose or damaged. If your gas cap is loose, tighten it and clear the code. Inspect your gas cap for physical damage or deterioration. However, it should be noted that damage to the gas cap or deterioration of its components is not always noticeable. If your gas cap was not loose and you do not see any indications of failure, try replacing the gas cap anyway and clearing the codes. Gas caps are relatively inexpensive and are often the fix for code P0446.
- If the fuel cap didn’t fix it, perform an EVAP system leak check: Pinch off the vent tube to the EVAP Vent Control Valve. Pressurize the EVAP system with an EVAP smoke machine leak checker. Check to see if you see any smoke leaking out from any hoses or seals. If there are any leaks, repair leaks and check to see if the concern is resolved.
- If you find no leaks, check the EVAP vent control valve for proper operation. This valve can get sticky, have debris caught in it, or the internal solenoid can fail and not operate. To test: Remove the EVAP vent control valve from the vehicle. (Tech Tip- The EVAP vent control valve is usually located under the car in the rear of the vehicle by or attached to the charcoal canister.) Verify with no power or ground supplied that you can blow through the valve’s openings. (If you can’t blow through the openings, the valve is stuck closed and needs to be replaced.) Now, supply power and ground to the solenoid (reference the service manual for your vehicle to find out which pins to supply power and ground to) the valve should click and now you shouldn’t be able to blow through the openings. If you can blow through the valve when it is powered on, then the valve is faulty and needs to be replaced.
- If at this point the vehicle is still setting the same code, you may have an electrical problem and will need to bring it to a shop to have further diagnostic work performed.
Estimated Cost of Repair
For error code P0446, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.
- Gas Cap $20-$60
- EVAP Line $20-$100
- EVAP Vent Control Valve $150-$200