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P0442 EVAP Emission Leak Detected – Causes & Fixes

In OBD2 Trouble Codes by Magnus SellénLeave a Comment

The EVAP system is designed to capture gasoline vapors through a charcoal pellet canister.

The vapors are then directed through a series of valves to the engine’s intake manifold. While driving, air is blown into the canister and the fuel vapors flow through the bleed control valve.

When the fuel vapors reach the combustion chamber, they are mixed with air and ignited. This sets the car in motion. The ECM is in constant communication with the vent control and purge valve. Occasionally the ECM closes both the vent control and purge valves, 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 with a diameter between 0.020 and 0.40 inches, error code P0442 will be displayed. EVAP error codes run from P0440 to P0457.

P0442 Symptoms

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

Causes of Error P0442 Code

  • Defective bleed 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 cap

Loose gas cap: The first thing you notice when you have a fuel leak is a strong smell of fuel. Many drivers sometimes forget to close the fuel cap after refueling. Before driving, make sure that the fuel cap is securely fastened. Also, inspect the fuel cap for physical damage.

A fuel cap is an inexpensive car part, and you can easily find a suitable one for your car in your garage. On some car models, the error code may be due to a dirty fuel cap. If the fuel cap is corroded, it may be difficult to close it. Once corrosion is detected, replace the entire fuel tank filler pipe and replace the damaged fuel cap O-rings.

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Cracked EVAP hoses: These are not easy to check 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. Inspect the hose connections closely.

Faulty purge and vent control valves: Sometimes the valves get clogged and sticky, which hinders their smooth operation. The first thing to do is to make sure that the valves have the correct tension. You will need a multimeter to do this.

Remove the valve plug and connect it to a multimeter. If it works well, you should have a 12-volt indicator when you switch it on. If it does not receive any voltage, you must check the wiring to the PCM. The purge valve solenoid can be checked using a vacuum pump.

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 on the rear quarter panel. The function of the canister is to store the fuel vapors and release them to the engine when the vehicle is running. This is done through constant communication between the bleed valve and the ECM, which determines when the valve opens and closes.

Most of the time, the EVAP works perfectly and requires little maintenance. However, the bleed and vent control valves can get stuck open, resulting in inefficient fuel consumption. Leaks in the fuel lines mean that fuel vapors are released into the environment. Most mechanics use a special smoke machine to detect small EVAP leaks. The smoke machine emits colored ultraviolet smoke that appears where there are leaks. You must also check the voltage of the venting magnet with an ohmmeter to make sure it is operating properly.

How to clear the code after fixing problems

When you have made sure that the gas cap is tightly closed or that the purge and vent valves are working optimally, error code P0442 will normally clear 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. Allow approximately one week for the vehicle to complete the EVAP checks. If the fault codes persist, carefully check the EVAP system components for signs of cracking. Check the O-rings for damage.

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The fault code refers to small leaks and it can be difficult to correct the problem immediately. The first place to check is often the gas cap, but if it is working well, you may need to perform vacuum tests to identify the source of the leaks.

Finding small leaks in the EVAP system is not easy. However, many mechanics will use a special smoke machine. The machine pumps a foggy mineral oil mist into the EVAP system, but at low pressure. When the mist circulates, it finds an outlet where there is a small leak. The mechanic can then seal the leak. To increase the efficiency of the smoke machine, a special ultraviolet dye is added to the machine, which is visible under a UV lamp.


The EVAP system is essential to trap fuel vapours and prevent them from escaping into the environment. At the heart of the EVAP system are the charcoal canister and the purge valves. The EVAP fault codes vary, but the P0442 is responsible for small leaks with diameters ranging from 0.20 to 0.40 inches.

This is difficult to detect and requires the use of a special smoke machine. In most cases, the main cause of EVAP error codes is a loose or defective fuel cap. But if after replacing the cap, you find that the fault codes have not yet been eliminated, you must carefully check your EVAP system for leaks.

The purge solenoid valve must be connected to an ohmmeter to ensure that it receives the correct voltage. Closer inspection may reveal cracked connection tubes. Hoses are under enormous pressure due to the high engine temperatures and are prone to cracking. If the error codes are not clear after all this, you must have the PCM checked for programming errors.

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