Auxiliary Emissions ControlOBD2 Codes

P0456 – Meaning, Causes, Symptoms, & Fixes

What Does Code P0456 Mean?

  • P0456 definition: Evaporative emission control system leak (small).
  • Issue Severity: LOW – Continued driving for a short period of time is okay
  • Repair Urgency: Get this fixed within the next month to prevent drivability problems and excessive fuel consumption.
  • Diagnosis: It is unlikely the driver will notice any symptoms with check engine light code P0456 other than a slight odor of fuel, a slight decrease in fuel economy, and the check engine light. However, as with all check engine lights, it is recommended that you get it fixed as soon as possible so the engine can be running at the proper specifications to prevent further damage.

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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 volume control valve. The vent control valve is usually open when the engine is at normal operating temperature, and the purge volume control valve is commanded on when the ECM is ready to burn the built-up fuel vapors. However, when the vehicle is turned off the ECM performs a leak test to ensure the evaporative emission control system is working properly. During the leak test, the ECM closes the vent control valve and purge valve to seal the evaporative system. If the EVAP system does not maintain the pressure, the ECM recognizes an evaporative emission control leak. In the case of P0456, it is a small leak, less than .020” in diameter.

P0456 Causes

There are many potential causes of code P0456.

  • Loose or damaged gas cap
  • Leaking or disconnected EVAP hose
  • Faulty purge volume control valve
  • Faulty canister vent control valve
  • Charcoal canister leak
  • Leaking fuel tank

P0456 Symptoms

  • Check Engine Light is on
  • Decreased fuel economy
  • Increased vehicle emissions
  • Fuel smell

How Do I Fix Code P0456?

With an EVAP fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby 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 P0456?

P0456 can be caused by anything from a loose gas cap to a faulty valve to a leaking fuel tank. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

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 P0456 code.

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Possible Repair Costs for P0456

For error code P0456, 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 Purge Volume Control Valve $150-$200
  • Charcoal Canister Vent Control Valve $150-$200
  • Replacement Evap Line $50-$100
  • Charcoal Canister $200-$600

DIY Steps to Diagnose Code P0456

Engine code P0456 could be caused by a number of things, including a loose gas cap, a faulty valve, or a leaking fuel tank. If you’d like to try to fix code P0456 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind this is an intermediate-level diagnosis and repair and not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

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

  • FIXD
  • Fused power wire
  • Ground wire


Scan your vehicle to verify P0456 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 P0456.


Check for cracked or disconnected EVAP hoses near or connected to the engine air box. Replace cracked/disconnected hoses. Clear the code.


Inspect the fuel tank and charcoal canister for damage and leaks. Replace if necessary.


Check the purge volume control valve for proper operation. This valve is normally not powered on and when at rest, with no power source applied, does not allow air to pass through. It can get sticky, causing leaks. 

The purge volume control valve is usually under the hood near the airbox or intake manifold. To test, remove the hoses from either side of the purge volume control valve with the key and engine off. Blow through openings with no power supplied. If you can’t blow through them, they are sealing properly and are most likely not the cause of this medium EVAP leak.


Check the charcoal canister vent control valve for proper operation. This valve is normally not powered on and when at rest, with no power source applied, allows air to pass through. It can get sticky, causing leaks, or the internal solenoid can fail and not operate properly. 

The charcoal canister vent control valve is usually connected to the charcoal canister underneath the vehicle. To test, remove the hoses from either side of the charcoal canister vent control valve with the key and engine off, unplug it from the vehicle, and remove it from the vehicle. Blow through openings with no power supplied. Air should pass through. Now, supply a fused power source to one side and ground to the other of the electrical connector. Blow through the openings again. If you can’t blow through them, they are sealing properly and are most likely not the cause of this medium EVAP leak.


The leak causing code P0456 is often too small to see. If you have completed all of the previous diagnostic steps, a smoke test may be necessary. You can purchase a smoke tester from Amazon to do it yourself, or you may want to take it to a shop to find the leak.

Common P0456 diagnosis mistakes

Many assume that a loose fuel cap is the only problem and do not perform all the tests necessary to diagnose the full EVAP system. The P0456 medium leak is a bit trickier to diagnose. Also, many manufacturers have technical service bulletins regarding EVAP codes. Be sure to check if your vehicle has any technical service bulletins available to save time diagnosing and/or misdiagnosing the car.

Still Need Help Fixing Code P0456?

If you’ve followed the steps above and are still experiencing check engine code P0456, 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.


Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

Justin Hughes
Recovering autocross and track day enthusiast. Once turned a VW Jetta into a pickup truck. Lives in a van down by the river. Dream car: 2001 Subaru WRC rally car.

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    1. Hi, I just want know dose this work for my car, the car I have it is Mercedes com 320, 2002

      1. Hi the Fix work for Mercedes clk 320, 2002

        1. Hi Mariam! Yes it will!

        2. I have a code 1456 on my Challenger Hellcat! I replaced the purge valve, gas cap, and canister! No luck I need help

          1. 2006 Jeep Grand Cherokee 3.7l
            I replaced my purge valve, vapor canister, leak detector, all seals and 2 gas caps.
            Then I heard something about reversing the gasket on the cap. That worked….. mileage also picked up 2 mpg.
            That’s what cost me about $600 +++. A rubber band. ###????!!!!!

            1. Questions is it a good idea to buy a car with evap code issues 2008 Jeep Grand Cherokee Laredo Sport?

        3. Is this covered on Kia Rio 2016 warranty at 37,000 miles?

          1. How does one clear the code. There are no other obstacles or “symptoms found. Can I clear the code myself?

            1. Yes Sally, once you scan you’re vehicle you’ll be able to see all the information about your problem written in plain English and you’ll also have the ability to clear your light. 🙂

      2. Hi Mariam,

        Yes, FIXD will work with your Mercedes!

      3. I have a 2013 Lincoln MKX with the code P0456 .. I don’t have a gas cap per se and I’m not familiar with where all the parts and places to look at. The YouTube videos I’ve seen are vague and not specific to my vechile. Please if anyone has a suggestion of where to look and what part would be very helpful.

    2. after u

      I remove & tighten gas cap on my2011 subaru forester how do I clear the code po456

      1. You can clear your Check Engine Light in the FIXD app from your mobile phone!

        1. I gave up trying to clear the check engine light on a 2012 Jeep liberty. Then engine was warm could this have something to do with why I could not clear it?

    3. My 2014 Ford Explorer does not have a gas cap. So does this mean the sensor has to be replaced?

      1. Hi Don,

        There are a number of different fixes to trouble code P0456. You can replace the sensor and clear the check engine light to see if it fixes the problem, but you may need to run tests to verify the source of the problem.

        The FIXD Team

      2. 07 jeep compass sport will this work

    4. 2017 Dodge Journey. Got P0456. Gas cap looks good. I hit the button to clear the check engine light, but it won’t clear it. It runs another scan and the light remains on.

      1. Hi David,

        There are multiple other possibilities for this Diagnostic Trouble Code to be set. The gas cap is the most common fix but not always the source of the problem. Please follow our diagnostic steps to pinpoint the source of your problem!

        Thank you,
        The FIXD Team

    5. My toyota sequoia has this code mechanic says the canister valve is closed and i need to replace it. But also said he doesnt have a certain smoker that the toyota dealer has a d i should take it to the dealer to have them smoke it to properly diagnos the issue. Should i take to toyota or should i just replace the canister? What if its not the canister?

      1. Hi Ruby,

        Our recommendation is to follow the diagnosis steps to pinpoint the issue in your vehicle. While replacing the whole canister valve could fix the issue, it is better to be safe than sorry and spending more money later on. Let us know what your problem was, we would love to hear it!

        The FIXD Team

    6. where do I find the hose I have a 2006 hy santa fe

    7. I got the P0456 code on my 2012 Jeep Patriot. Took it in to the dealership, and they replaced the damaged evap parts and replaced the gas cap. The light went off, but now it came back. Did the dealership not fix it properly, or does the app not recognize the fix?

      1. Hey Erika, So we recommend clearing the code with FIXD and then to try reading the codes again to see if P0456 comes up. If it does, then the issue is most likely not that the app doesn’t recognize the fix, but something else.

        Thanks, FIXD Team

    8. I got a Lexus ES 330 2004. I followed your advice to replace the fuel cap and cleared the engine light. But after running some miles, the engine light, VSC,m & TRAC OFF turns on again. I repeated the whole process but these lights keep coming back

      1. I have a 2006 Toyota 4Runner and the Check Engine and Trac lights come on. Fixd reported the P046 error. I tighten the gas cap and clear the check engine light. a couple hundred miles down the line the same thing happened. Is this error code also tied to the traction system?

        1. Mine turned out to be an oxygen sensor when I got those symptoms. It was a 2008 4Runner.
          No -one has been able to tell me why Toyota tied the V-Trac and other codes to the oxygen sensor. I think it was no better than a general “check engine” light.

    9. Will fixd work in any car or truck or just mine?

      1. Hey Ron! FIXD works with multiple vehicles as long as you connect each vehicle with the App!

        FIXD Team

    10. How often does the system perform a leak test? I replaced a damaged hose off the evap canister but I can’t clear the check engine light. Do I have to wait a certain amount of time before it will clear, or is there another problem?

      1. 2098.. P2096 land rover 5.0l hse.. Oxygen sensor its very good and no leaks or fix engine.. The odometer its 71k miles if deleted the check engine and start returning again if turn off and running if the engine hot or after 5 minutes.. I want help me

    11. My 2011 Ford Escape does not have a gas cap. The code was cleared twice but comes on intermittently every 5-7 days. Any suggestions?

    12. 2008 Jeep Wrangler. Right before my EVAP light came on, the gas pump did not shut off and gas spilled over. Same thing occurred after the EVAP light was on at the next trip to the pump. Coincidence, cause, or symptom? Any thoughts?

    13. Very good article – Thank you! I have BMW X5 2001. In addition to P0456 i also have codes P0171 & P0174 (System too lean). Are those due to the same reason?
      Will the P0456 impact the SMOG check?

    14. I have a 2007 dodge magnum 3.5 engine won’t start at times after driving batter is new alternator good have a po456 engine code engine light is on

    15. How to clear code PO456? Still show on my nissan sentra 2014 dash board fuel cap loose

    16. I have a 2008 Audi convertible. The PO456 came on. Fixed diagnosed it. How do you clear the code?

    17. 2000 isuzu redeo
      What I can do to fix

    18. I have a 2007 prius and the dealer said the evap system is leaking where it connects to the gas tank and the it is built into the gas tank and I need a new gas tank and evap system for $1800+. I was thinking of getting some Flex Seal Spray Rubber Sealant Coating and spraying the evap system on the top of the tank to see if it stops the leak. Is this a good idea?

      1. Hey Dave, did this fix your problem? I was thinking of trying the same thing!! I also have a 2007 Prius in which I was told the same by an independent shop except they said the tank was ok. They want $550 to replace the fuel filler pipe alone, that’s after charging me $310 for the canister vent control valve. The car came from Vermont and is pretty rusty underneath so I hate to keep spending money in it. Thanks!

    19. Fixd is very helpful and useful it keeps alot of unnecessary fears about my car. No more worrying i have fixd

      1. That brightens our day to hear, Curtis! Thank you so much for the kind words and using FIXD. Happy and safe driving! 🙂

    20. is ok after fix the po456 code ,to erase the engine light disconnecting the batery for 15 seconds?.

      1. Hi Jose, FIXD lets you reset your check engine light. Once you scan you’ll be able to see all the information about your problem written in plain English and you’ll also have the ability to clear your light.

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