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P0442 – Meaning, Causes, Symptoms, & Fixes


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What Does Code P0442 Mean?

  • P0442 definition: Evaporative emission control system leak (medium).
  • 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 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. A driving duration with this problem of even just a few weeks can damage other engine system components.
  • Quick tips: Use the FIXD Sensor and app to diagnose P0442 yourself, see the most likely fix and cost for this diagnostic trouble code, access our Mechanic Hotline, and more.

The evaporative emission control system (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 an EVAP system leak test to ensure the evaporative emission control system is working properly. During the system 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 during the test, the ECM recognizes an evaporative emission control system leak. In the case of P0442, it is a medium-sized leak, between .020”-.040” in diameter as opposed to a small leak (P0456), less than .02” in diameter or a large leak (P0455), larger than .04″ in diameter. Car with medium EVAP system leaks show very few symptoms much like those with a small leak.

P0442 Causes

There are many potential causes of diagnostic trouble 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

P0442 Symptoms

How Do I Fix Trouble Code an EVAP Leak?

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

The FIXD Sensor and app can help you diagnose and fix P0442 yourself by giving you access to detailed engine diagnostics information that is easy to understand (even if you don’t know cars) –  live OBD2 data is also included and incredibly useful for diagnosis (and the Mechanic Hotline is included in premium too if you get it). You can even use FIXD to clear the fault codes on your vehicle and see if your fix worked, or simply turn off codes that aren’t serious.

> Click here to get FIXD for $19.99 for a limited time!

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.

How Much Does It Cost to Fix an EVAP System Leak?

P0442 can be caused by anything from a loose gas cap to a faulty valve to a leaking fuel tank. A Medium leak (P0442) or small leak (P0456) wouldn’t be as commonly associated with a loose gas cap as P0455, a large leak. But, you should look at all of your options to ensure you identify the actual repair necessary. It can save you a lot of money. For instance, a gas cap related problem might cost $0-$60 (it might just be loose), a fuel tank, or faulty valve however aren’t as kind to your bank account balance. Fixing the most likely cause is vital, but, when comparing potential fixes also take into account how much the repair costs are, whether you are capable of doing the repair, and how reversible it is if done improperly (The last 2 are probably only important for DIY. Things go wrong, especially when you are learning).

Directionless part replacement or replacements based on information sources of questionable accuracy, result in spending money on parts you don’t need. An accurate diagnoses is necessary for both estimating cost and ensuring you perform repair on the right part the first time. A good diagnosis can actually save you money, whether you do it or a mechanic does.

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 P0442 trouble code.

Possible Repair Costs for P0442

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 (If the cap’s just loose, tighten it – $0 repair)
  • 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 P0442

Engine code P0442 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 your EVAP System leak 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 with the FIXD Sensor and app 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.


Luckily this first part takes a couple minutes to check. 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 (Medium EVAP System Leak).


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 a EVAP system leak. 

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, the part passed the test. If you can’t blow through them, it indicates that 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 P0442 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 test for the leak.

Common P0442 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 system 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 P0442?

If you’ve followed the steps above and are still experiencing check engine code P0442, 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. Don’t have a FIXD Sensor yet? Click here to get yours for just $19.99, including a free 14-day trial of FIXD Premium!

Popular Engine Codes P0420 P0172 P00171 P0128 P0300 P0456 P0430 P0442 P0455 P0113

Fixed It But The Check Engine Light Is Still On?

Check engine light sometimes need to be reset manually, check out our article:

How to Reset Your Check Engine Light | 4 Ways To Clear It (With or Without a Scanner)

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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About the Author

Justin Hughes

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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