Auxiliary Emissions ControlOBD2 Codes

P0442 – Meaning, Causes, Symptoms, & Fixes

P0442 evaporative emission control system leak (small)
Reading Time: 4 minutes


Code P0442 Definition

Evaporative emission control system leak (medium).

What Does Code P0442 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 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 P0442, it is a medium-sized leak, between .020”-.040” in diameter.

What Are The Symptoms Of Code P0442?

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

What Is The Cause Of Code P0442?

  • 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

How Serious Is Code P0442? – Low 

It is unlikely the driver will notice any symptoms with check engine light code P0442 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.

Code P0442 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 P0442 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.

Tools Needed to Diagnose:

  • FIXD
  • Fused power wire
  • Ground wire

How To Diagnose And Repair Code P0442?

Difficulty of Diagnosis and Repair – (3 out of 5)

  1. Scan your vehicle to verify P0442 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.
  2. 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 P0442.
  3. Check for cracked or disconnected EVAP hoses near or connected to the engine air box. Replace cracked/disconnected hoses. Clear code
  4. Inspect the fuel tank and charcoal canister for damage and leaks. Replace if necessary.
  5. 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. To test: Remove 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. (Tech Tip- The purge volume control valve is usually under the hood near the airbox or intake manifold.)
  6. 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. To test: Remove 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. (Tech Tip- The charcoal canister vent control valve is usually connected to the charcoal canister underneath the vehicle.)
  7. The leak causing code P0442 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.

Estimated Cost of Repair 

For error code P0442, 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


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  1. I am debating on whether to look for a new car toward the end of the year, depending on how expensive the emissions repair will be. My 2000 Malibu will not pass inspection this July. Where can I get the repair done at reasonable price, please?
    Thank you

    1. Hi Mary!

      You can actually use the FIXD app to look for a repair shop near you!

    2. This is relatively inexpensive to repair ?

      1. Tried gas cap and a few of the other ideas given to me by this app like checking some of houses going to charcoal can etc. Hit the reset light and it is still on. Can I get a sticker in NH with this on

    3. Want to clear check engine light

      1. How do I clear the engine light from my 2004 T-Bird?

        1. To all asking about clearing the error code: After a few days the check engine light will return unless the problem is fixed. Clearing the code does nothing but get the amber light out of your face for a short while…

          1. Indeed, Michael. If the code is cleared but the issue with the vehicle is not resolved, the check engine light may reappear after a certain number of miles have been driven.

            If the code is emissions related, FIXD cannot clear it due to Federal Regulations. You must get the issue fixed and then the code will be cleared after 30 miles of driving. If it is not emissions related, please reach out to us via email at .

  2. How can I turn off the check engine light?

    1. Hi Alan,

      Our sensor (FIXD) connects to an app on your phone and allows you to learn more about your Check Engine Light, provides an explanation of your trouble code in simple and understandable terms, and also gives you the ability to turn your Check Engine Light off.

    2. How do I turn off the engine light

      1. Hi David,

        You are able to clear your Check Engine Light with the FIXD OBD-ii sensor and the FIXD mobile application!

        The FIXD Team

        1. Hi Team, we had a lot of work done on our car two days ago. It all had to do with the axels, tie rods, hub barrens, radiator replaced, etc. could this have caused damage to make the Check engine light come on?

          1. I would have to say a confident “No” to your Question..

      2. Where do you clear the light? I see it says it can be done but I don’t see that option anywhere in the app.

        1. When the code comes up, check the bottom of the page. Has a clear code button.

          1. It presents as a wide rectangular red background with the words clear check engine light.

    3. How do I turn the check engine lift off and what is the cost to repair?

  3. My 2018 GMC Canyon has the P0442 indication which implies a loose gas cap but it doe not have a gas cap? It only has 700 + miles.

    1. Hi Mark,

      The usual fix for trouble code P0442 is a loose or damaged gas cap but there are other possibilities as well. You may need to run a few tests to pinpoint the problem.

      The FIXD Team

    2. Hello. I had the problem fixed in July and the check engine light is back on again. Should they charge me again for the same problem?

    3. If you only have 700 plus miles on your Truck. Then take it to where you bought it. It’s still very much under Factory Warranty..

  4. Using FIXD, code 0442. Is there anyway to find out if any of the components of the Evap system is malfunctioning just by looking in the information given by FIXD when communicating with car computer?

    1. Hi Zeke,

      It is possible to monitor the tank pressure to confirm if a leak is present or not. This will be dependent on your vehicle specific repair manual on what this value should be. Let us know if you find the issue!

      The FIXD Team

      1. How do I repair?

      2. How do you monitor the tank pressure?

    2. I have done all of what is recommened, even a rebuilt motor and transmission in a 2001 Chevy Blazer. Enough is enough. What can I do?

  5. If I clear this code and a problem still exists, will the check engine light come back on?

    1. Yes, it may take a day or two but if the issue isn’t resolved the check engine light will turn back on!

    2. Yes

  6. If I clear this code, and a problem still exists, will the check engine light come back on?

    1. Check engine lights illuminates due to system failure in the EVAP systems. Something loose or failure of purge valve holding pressure can cause this to happen. You can change this yourself look on YouTube buy the part, it’s in expensive while auto shops will charge you ridiculous amount of price of around $400-$600 for a $20-$30 part.

  7. Yes, after about 125 miles of driving.

  8. I don’t see in the app a place to clear the code. Can you explain where this is in the app please

    1. Hey Jenifer!
      Try hitting the Diagnostic Report button after scanning for codes. Once that page is done loading, there should be an option at the bottom of the page to clear the codes. Be sure not to try and clear just one specific code, but actually all of the codes that have come up.

      FIXD Team

  9. I had the P0442 code show up on my 2006 Volvo V70. Replaced the gas cap as suggested, light came back on. Took the car to a repair shop I had used in the past, they claimed it was a crack in a hose and that they had “sealed” and I should not have any more problems. Check engine light came back on after about 10 miles. I called them back and was told I would probably have to replace the entire evap system, 600-800.00 but the parts were no available and on back order. I then took the car to the volvo dealer. Spent 4 hours and was told they did not see any obvious leaks in the system would need to do a smoke test. Both told me it was ok to continue to drive the car should not be a problem. I am at a loss as to what to do. I got the feeling neither place wanted to fix the problem. Any suggestions? I do not want to keep paying for someone to look at the car just to be told they cannot find anything.

    1. I know you posted this back in Jan., if you haven’t gotten it repaired yet start replacing your air lines to your air intake box-your car is just old enough for these type hoses to split on the ends – if the rest of the hose looks good just cut off 1/4 or 1/2 inch off the bad end and plug it back on. I know this from experience, lol….

    2. Hi Joanne, buy some MAP cleaner and spray your sensor in the air flow by your air filter by taking air filter apart and new filter ? It helped mine ! Good luck

  10. From my experience 0442 small leak gas cap. I have a GM car (Cadillac) and I had replaced the gas cap and the check engine light came back on. I replaced the new gas cap with a new gas cap. I shut the light off and it came back on. I replaced the new gas cap with another new gas cap and the light stayed off. I believe the certain new gas caps that are faulty from the factory. I went thru 3 new gas caps before I found one that worked.

  11. I have just put on my second OEM replacement gas cap to see if the code remains off. So this makes three. Lets see if this does the trick. Gas caps are the least expensive part and easiest to change.

  12. I have click on on Clear the Code for a po452 but it will not clear. What next?

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