Auxiliary Emissions ControlOBD2 Codes

P0446 – Meaning, Causes, Symptoms, & Fixes

p0446

What Does Code P0446 Mean?

  • P0446 definition: Evaporative Emission Control System Vent Control Circuit Malfunction
  • Issue Severity: LOW– Continued driving for a short period of time is okay.
  • Repair Urgency:  Get this code fixed withing the next month to prevent issues related to the emissions system including failed inspections.
  • Diagnosis: It is important to complete the entire diagnostic process when diagnosing the P0446 code. This DTC can be triggered by just about anything in your vehicle’s EVAP system from a loose gas cap to a defective part

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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.

P0446 Causes

  • 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

P0446 Symptoms

  • Check Engine Light is on
  • A slight decrease in fuel economy
  • Gasoline smell
  • Commonly associated with error codes: P0440, P0441, P0442, P0443, P0449

How Do I Fix Code P0446?

With a P0446 code, the first step is to get it properly diagnosed to figure out what is causing the malfunction in the EVAP system. Using the live data function of the FIXD sensor and app allows you to read and analyze fuel trims to properly diagnose a P0172 code.

If your engine is running lean and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal-certified shop to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0446?

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0172 code.

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Possible Repair Costs for P0446

When it comes to making repairs associated with the P0446 code, 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. 

  • Loose/damaged gas cap
  • EVAP hoses
  • Fuel tank
  • Charcoal canister
  • Faulty vent control valve
  • Faulty purge control valve

DIY Steps to Diagnose Code P0446

If you’d like to try to fix code P0446 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Diagnosis can require some specialized equipment beyond what the FIXD Sensor can provide, but this is usually still a beginner-level diagnosis. 

DIY difficulty level: Easy

This repair is simple enough for beginners to attempt.

Tools/parts needed (our top picks from Amazon):

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Use FIXD to scan your vehicle to verify P0446 is the only code present. If other codes are present, they must be addressed first. If it is paired with P0441 and/or P0440, there is most likely a solenoid failure, leaking charcoal canister, or a more complex EVAP leak.

STEP 2: INSPECT GAS CAP. 

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.

STEP 3: PERFORM EVAP SYSTEM LEAK CHECK.

If the fuel cap didn’t fix it, perform an EVAP system leak check. To do this, 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.

STEP 4: CHECK EVAP VENT CONTROL VALVE.

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.

STEP 5: CONSULT A PROFESSIONAL.

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.  

Common P0446 diagnosis mistakes

It is important to complete the entire diagnostic process when diagnosing P0446. Don’t overlook a loose or faulty gas cap as this is the most common culprit that cause the check engine light to come on for this code.

Still Need Help Fixing Code P0446?

If you’ve followed the steps above and are still experiencing a lean engine condition and code P0446, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

Jeffrey-Ross

Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

Jeffrey N. Ross
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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41 Comments

  1. Already took care of it, the pressure/purge sensor on top of the fuel tank wasn’t functioning

    1. Good to hear Marc!

      1. Can I fix this myself?

        1. Thanks for all the tips and advice. I just went ahead and replaced the purge valve. Of course the mounting bolt broke off. Bench tested the old solenoid and it was intermitten holding. Think I got it.

      2. My 07 H2 had that issue so I replaced the canister (ta-dah. All is good). One week later we had a tropical storm and major flooding… can’t avoid every pothole filled with water (Come on I live in Jersey!) Service engine light again and code P0446. Can the flooding potholes effect my canister?

    2. This tool is the greatest thing I ever bought you guys are great

      1. Thanks Bobby! We appreciate it!

        FIXD Team

    3. How did you figure out this specific problem?

  2. I just got this code on my car is it still safe to drive until I can repair? Will that cause car to cut off?

    1. Hello,

      The trouble code P0446 will not give you any drivability issues, but just like all check engine lights, it should be repaired as soon as possible.

      The FIXD Team

    2. I took my car with more than two mechanics, each one was saying something, I didn’t know exactly where the defect is, but with this FIXD sensor I knew where the problem is, thank you Fixd I love it!

      1. That makes us so happy to hear, Amanuel! We are so glad that we were able to help you know what is going on with your car to protect you from unnecessary repairs. Happy and safe driving 🙂

    3. My check engine light won’t come on when I turn the key and I can’t pass the emissions test

      1. unplug the battery for 10 minutes then plug it back, that will clear all the Check Engine Light, then take the car to the emission test.
        I’ve done that when I had my code 0446 with Check Engine Light on before I bought FIXD, nowadays I use FIXD to turn Check Engine Light off with ease.
        Hope that helps

  3. I’m still getting a P0446 code and haven’t been able to figure out why. I’ve installed a new gas cap, vent solenoid valve. Purge valve and pressure sensor unit on the fuel tank and still get the P0446 code. Any ideas?

    1. Hi Darrell,

      There are a number of possibilities of this trouble code and it’s awesome to hear that you’ve eliminated a few already! Before moving forward I would advise that you run tests to make sure you need to replace the parts or not. Check out this video on diagnosing and finding your issue!

      If you still run into problems you may need to go to a mechanic.

      Thank you,
      The FIXD Team

  4. FIXD is such a great thing. Thank you so much. I’ve used it several times for problems on my car and work van. They have been 100% right. Every time. Saved me tons of money. But most of all. Saved me aggravation. Love it !!!

  5. I hav a 2006 Chevy 3500 Express RV conversion. My generator runs on fuel from my tank. Everything else checks out. Any ideas?

  6. Took my Buick Century in, they did a smoke test and it was repaired ($400 for parts including a new gas cap), the code came back; the mechanics took a second look and said a purge valve o-ring was stiff and wasn’t sealing, said the cost was $35 to fix that….makes me wonder if the $400 for the evap solenoid and new gas cap was really needed.

  7. Got a po446 code. Put on new gas cap, changed evap, even got cadillac converter checked, code wont clear. 2006 cadillac dts.

  8. I have a 2008 Ford F-150 4.6liter engine,I replaced the intake manifold because it was leaking and after I replaced the code p0446and p0452 codes came up on the check engine light also it shakes when I’m driving and don’t have the same power.

  9. I took my brothers Chevy silveraldo and had it hooked up to diagnostic and two codes came up. One I pretty much understand with thermostat. But this evaporative emission system vent control circuit has me in a pickle. My question is call I still drive it until I can get it fixed? Thsnks

  10. I had an issue where I popped a few fuses and relays, I want to double check this particular relay or fuse, but can’t figure out which ones to check.

  11. Hi
    I have P0441,p0442 and P0446 showing on my Lexus RX .
    Please should I do.

    Regards

  12. Could this issue have anything to do with the Coolant Reservoir?

    1. No, coolant reservoir is only used with the radiator

  13. Lexus ES 300 – got the only code p0446. replaced with a new evap canister assembly . After driving for about 6 months the same code came again. what else would cause this single code.

    1. What if you are getting the P0446 code and
      the Tahoe is hard to start after putting gas in the tank??

      1. I have that on my Silverado; they diagnosed it as fuel pump and are replacing the fuel pump today.

      2. On my 2004 Sierra replacing the Purge Valve in the Intake Manifold fixed this same problem.

      3. I was having this problem on my 2008 Chevy Malibu. Replacing the purge valve fixed the problem.

  14. I have a 1998 Chevy Silverado C1500 (5.7L). Getting codes P0446 and P1441 Where does this point to for the fix assuming that maybe one problem is causing both codes?

  15. I had issues with not being able to fill up my tank w/out it clicking off 100 times. 15+ min to fill-up my tank was getting out of hand. So, I looked up this symptom and it suggested the evap canister needs to be replaced. Mind you, no code had ever shown up, but I replaced the darn thing for $600 for the part. Pretty easy swap. Anyhow, I’m still getting the same symptom at the pump; which is quite annoying; and still, no “check engine” light. S.O.S!!! Thoughts?

    1. My 2004 Chevy Suburban 1500 is impossible to fill at the pump without babying it and keeps giving me the P0446 code. I watched a zillion videos on these symptoms all pointing to the evap canister, purge valve solenoid and vent filter solenoid. The purge valve solenoid tested good and I replaced the vent filter solenoid. I also removed the canister and checked for any loose charcoal that might have made it’s way into any of the vent lines causing a clog, it looked ok. The only other part of the system I haven’t checked is the pressure sensor on the top of the tank(which I don’t want to mess with if possible). And from what I understand, it wouldn’t cause the to be hard to fill anyway. I am going to remove the vent line from the fuel tank to the evap canister and try to fill the tank with fuel.
      Stay tuned!!

      1. Just got back from the gas pump and filling problem is gone. My next step will be to reconnect the fuel tank vent hose to the charcoal canister and disconnect the hose that leads to the evap vent filter solenoid. My next fill up should isolate wether I need to replace the charcoal canister or continue the diagnostic process.

        1. My 2011 Suburban is incredibly difficult to fill up. It will take about half a gallon before clicking off and that’s if it’s barely going in. Takes 10 minutes or longer to fill the tank. Its been doing this for almost a year but I never had a code until yesterday. Hopefully I can get it resolved soon.

  16. Check engine lite came on, replaced all hoses on Evap canister and gas cap, reset the flag, all is well
    your fixd module works great

  17. my 2006 ford explorer has gone into like a limp mode twice the only code i get is a po0446 any ideas thx.

    1. Fixd is so good that I figure out the engine light up issue. I replaced the gasket of fuel cap and clear the engine light. That is it. Thanks Fixd team. You have been giving me big help.

      1. You’re so welcome, Charlie! Thank you so much for the kind words and for using FIXD. 🙂 Happy and safe driving!

  18. Hi , I’m having a p0446 vent valve circuit mal function, and I have replace so far gas cap, purge valve, vent valve, canister is good , no luck!!! What could be the cause the trigger this code? Please any help will be appreciated (Chevy s10 2003 v6 vortec)

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