P0456 – Meaning, Causes, Symptoms, & Fixes

Code P0456 Definition

Evaporative emission control system leak (small).

Code P0456 Meaning

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. Both the vent control valve and the purge valve are usually open when the engine is at normal operating temperature. However, the ECM occasionally performs leak tests 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 create a vacuum. 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 sized leak, smaller than .020” in diameter.

P0456 Symptoms

  • Check Engine Light is on
  • Decreased fuel economy
  • Fuel smell

P0456 Causes

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

Code P0456 Severity – Low    

It is unlikely the driver will notice any symptoms with check engine light code P0456 other than a slight odor of fuel, decreased 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.

Code P0456 Common 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 small leak is a bit trickier to diagnose. Also, many manufactures 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.

Code P0456 Diagnosis Steps

How To Diagnose P0456

  1. 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.
    1. 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.
  2. Inspect your gas cap to see if it is loose or damaged
    1. If your gas cap is loose, tighten it and clear the code.
    2. 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 are not always noticeable. If your gas cap was not loose and you do not see any indications of failure, try replacing the gas cap anyways and clearing the codes. Gas caps are relatively inexpensive and are often the fix for code P0456.
  3. Check for cracked or disconnected EVAP hoses near or connected to engine air box
    1. Replace cracked/disconnected hoses
    2. Clear code
  4. Inspect the fuel tank and charcoal canister for damage and leaks. Replace if necessary.
  5. Check both the charcoal canister vent valve and purge valve for proper operation. These valves can get sticky causing leaks or the internal solenoid can fail and not operate. To test:
    1. Disconnect the valve connector and test that the valve is receiving power with a multimeter
      1. If there is no power, there is most likely a wiring problem or a faulty powertrain control module.
      2. Tech Tip- The canister vent valve is usually located under the car in the rear of vehicle by or attached to the charcoal canister. The purge valves are usually under the hood near the airbox or intake manifold.
  6. The leak causing code P0456 is often too small to see. If you have completed all of these 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.

Was this post helpful?

Comments 29


April 13, 2018

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


April 13, 2018

Hi the Fix work for Mercedes clk 320, 2002

Mason Mayes

April 16, 2018

Hi Mariam! Yes it will!

Mason Mayes

April 16, 2018

Hi Mariam,

Yes, FIXD will work with your Mercedes!


May 18, 2019

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.

J Talley

June 18, 2018

after u

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

FIXD Marketing

June 25, 2018

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

Garry Edwards

August 20, 2018

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?


July 7, 2018

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

FIXD Marketing

July 9, 2018

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


July 22, 2018

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.

FIXD Marketing

July 25, 2018

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


August 1, 2018

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?

FIXD Marketing

August 3, 2018

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


September 10, 2018

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

Erika Armstrong

September 27, 2018

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?

FIXD Marketing

September 28, 2018

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


October 19, 2018

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


January 3, 2019

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?


November 22, 2018

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

FIXD Marketing

November 27, 2018

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



November 24, 2018

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?

Steve Horvath

January 3, 2019

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?


January 14, 2019

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?


March 16, 2019

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?

Robert L White

June 14, 2019

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


July 1, 2019

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


July 12, 2019

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


August 14, 2019

2000 isuzu redeo
What I can do to fix

en English