P0442 EVAP Emission Leak Detected – Causes & Fixes

In OBD2 Trouble Codes by Magnus SellénLeave a Comment

flashing check engine lightThe EVAP system is designed to capture gasoline vapors through a charcoal pellet canister.

The vapors are then channeled through a set of valves to the engine’s intake manifold. When you are driving the car, air will be blown to the canister and the fuel vapors will flow through the vent control valve.

When the fuel vapors reach the combustion chamber, they are mixed with air and ignited. This causes the car to move. The ECM is in constant communication with the vent control and purge valve. Occasionally, the ECM will close both the vent and purge valve thus creating a vacuum. This is done to detect any leaks in the EVAP system.

Pressure should be maintained between the two valves and if the ECM detects a leak of between .020 and 0.40 inches in diameter, the error code P0442 will be displayed. EVAP error codes run from P0440 to P0457.

How the EVAP system works

The main component of the EVAP system is the charcoal canister. It is often mounted and hidden somewhere near the engine or at the rear quarter panel. The function of the canister is to store the fuel vapors and release them to the engine when the car is running. This is done through constant communication between the purge valve and the ECM – which determines when the valve opens and closes.

Most of the time the EVAP will work fine and requires little maintenance. But, the purge and vent control valves do get stuck open causing fuel inefficiencies. Leaks from the fuel lines means that fuel vapors find themselves into the environment. Most of the mechanics use a special smoke machine to detect small EVAP leaks. The smoke machine emits dyed ultraviolent smoke that shows up where there are leaks. You will also need to check the voltage of the vent solenoid with an ohmmeter for working condition.

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Symptoms of error code P0442

  • Strong gasoline smell
  • A decline in fuel efficiency
  • Check engine light turns on

Causes of Error P0442 Code

  • Defective purge and vent control valves
  • Damaged gas cap
  • A leak in the charcoal canister leak
  • Leaking EVAP hoses
  • Leaks in the main fuel tanks

Fixes of error P0442

fuel filler capLoose gas cap: The first thing you will notice when you have a fuel leak is a strong fuel smell. Many motorists sometimes forget to close the gas cap after refueling. Ensure the gas cap is securely fixed in place before driving. Also, inspect the gas cap for physical damage.

A gas cap is an inexpensive car component and you can easily find one suitable for your car at your auto repair shop. In some car models, the error code can be as a result of a dirty gas cap. If the gas cap is corroded then it can be difficult trying to close it. Once corrosion is detected you should replace the entire fuel tank filler pipe and replace damaged gas cap O-rings.

Cracked EVAP hoses: These are not easy to inspect for leaks. Since the leak is small, you may need to perform a smoke test to find the source of the leaks in the EVAP hoses. Make a closer inspection of the hose connections.

Faulty purge and vent control valves: Sometimes the valves get clogged and become sticky hindering their smooth operation. The first thing you need to ensure is that the valves are receiving the right amount of voltage. You will need a multimeter for this.

Remove the valve connector and connect it with a multimeter, if it is working fine you should have a reading of 12v when turned on. If it is not receiving power, you need to check the wiring to the PCM. Inspection for the purge valve solenoid can be done through the use of a vacuum pump.

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How to clear the code after fixing problems

Once you have ensured that the gas cap is closed tight or the vent and purge valves are operating optimally, the error code P0442 will normally clear by itself after a while. If this does not work you may need to disconnect the battery or use a diagnostic tool to clear the error. Give the car about a week for it to perform EVAP checks. If the error codes persist, carefully inspect the EVAP systems components for signs of tear. Check the O-rings for damage.

The error code relates to small leaks and it can be hard to fix the problem immediately. The first place to check is often the gas cap but, if this is working well you may need to perform vacuum tests to identify the source of the leaks.

Finding for small leaks in the EVAP system is not easy. However, many mechanics will use a special smoke machine. The machine pumps a misty mineral oil fog into the EVAP system but under low pressure. As the mist circulates it will find an outlet where there is a small leak. The mechanic can then seal the leak. To enhance the efficiency of the smoke machine a special ultraviolet dye is added to the machine and this is visible under a UV lamp.


The EVAP system is vital from capturing fuel vapors and preventing them from finding their way into the environment. At the heart of the EVAP system are the charcoal canister and purge valves. EVAP error codes vary but the P0442 is responsible for small leaks of between 0.20 to 0.40 inches in diameter.

This is hard to detect and require the use of a special smoke machine. Most of the time drivers detect EVAP error codes the main culprit is usually a loose or defective gas cap. But, after replacing this and you still notice that the error codes have not cleared you to need to carefully inspect your EVAP system for leaks.

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The purge solenoid needs to be connected to an ohmmeter to ensure it is receiving the right voltage. Closer inspection may reveal cracked connection hoses. Hoses are under enormous pressure due to the high engine temperatures and are susceptible to cracks. If the error codes do not clear after doing all this, you will need to have the PCM examined for programming errors.

Hello I'm Magnus, the owner and the writer of this website. I have been working with cars since I was 16 and I'm specialized with in-depth Automotive diagnostics. Also been driving drifting for the last 6 years. I'm here to give you answers to all your automotive questions and I hope that you enjoy our content.

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