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Code P0442. Evaporative Emissions Control System Leak Detected

Have a fault associated with code P0442 It can be really frustrating to deal with. Vacuum leaks in the EVAP system They are a real headache to find and diagnose correctly. You could spend hours and hours searching for them in vain.

That is why you need to learn to diagnose that fault in the correct way. And by this, we mean using a little ingenuity and understanding of how everything works in your car.

We are going to help you with it.

How Does The EVAP System Work?

Let’s see how this EVAP system works in general. What is this system and what is its function in the car?

The EVAP is an abbreviation of the phrase Evaporative Emissions Control System. This is a special emissions control system that is equipped for our cars.

This system has a special role, and that is to collect all the gases that are inside the gasoline tank and redirect them to the intake manifold so that they are part of the combustion process.

This means that this system extends from the rear, where the fuel tank is located, to the front of the car, where the intake is located.

This system is necessary to maximize emissions reduction. As you know, fuel evaporates and it is necessary to pressurize the fuel tank if you want to prevent these vapors from escaping into the atmosphere and contaminating.

The gases are piped from the gas tank to something known as a charcoal canister where they are purified and then sent to the intake manifold.

But between the inlet and the charcoal canister, there is a valve. Also known as a purge valve. This valve opens. Then, when there is enough vacuum, this system will open and the valve will bleed the gases into the engine.

But sometimes things don’t work as they should and unfortunately, the system doesn’t work properly. Therefore, it is very likely that you will get a check engine light and the P0442 code activated.

What is Code P0442?

The definition of this code is “Evaporative emissions system leak” or “Evaporative emissions control system leak detected“.

Well, this means that you have a vacuum leak in your EVAP system. Something is not sealing properly in this system, the PCM has detected this problem and activated the check engine light.

Even though a check engine light is activated, it doesn’t mean you have a serious problem. It’s just a small leak.

DTC code P0442 tells you that there is a leak somewhere in your evaporative emissions control system. This code does not identify a specific location. This makes the code somewhat difficult to diagnose.

What is useful for you to know are the causes of why this leak appeared in the first place. To find out what could cause this problem with code P0442 and continue from there.

Although P0442 does not indicate a serious problem, you should fix it before your next inspection.

Causes of Code P0442

Knowing the causes will be extremely useful for you as an owner because you will know where to look and quickly discover this problem. That is why you should follow us carefully until we cover all the possibilities that exist for this problem.

1. Damaged or Loose Gas Cap

One of the simplest things that could trigger a check engine light is the code P0442 It’s the gas cap. Even on some gas caps, there is a warning that you should tighten them if you want to avoid a check engine light.

So the first thing you should do is check the gas cap. You know where it is, just make sure it’s tight. Then delete the codes and see if they don’t appear again.

If the code still appears, it could be because you have a bad gas cap or a bad filler neck. It is best to clean it of the debris and try again.

Otherwise, you must replace it with a new OEM gas cap.

You may also be interested in Code P0446. Causes, Symptoms, Diagnosis and Repair

2. Damaged Fuel Pump Seal

The next possibility we would like to cover is the fuel pump. More precisely, the stamp is located between the fuel pump and the fuel tank.

This joint must seal 100% and not allow vapors to escape into the atmosphere. If this seal does not do its job correctly, P0442 or any other code connected to the EVAP system is activated.

Therefore, it is often recommended that you check this seal if you think everything else is sealed well.


The third very common cause of code P0442 is the leak in EVAP system hoses. All of these hoses are made of rubber and as the rubber ages, it begins to deteriorate.

This deterioration will cause the rubber to harden and crack. Fortunately, these hoses are not difficult to obtain or install. You can carry out this repair yourself and it will not be expensive.

4. Faulty EVAP Vent Valve

This vent valve works in conjunction with the purge valve. But unlike the purge valve, the vent valve allows air to enter and exit the charcoal canister.

This valve, like the purge valve, works with the help of a vacuum and this unit is basically a solenoid. Which means it is a closed loop.

Each time it fails, it could cause a check engine light and code P0442 or another code related more precisely to this component.

So, whenever you have the P0442 code and have a problem with your emissions system, it is worth testing this component with a multimeter and seeing if it works or not.

5. Faulty EVAP Purge Valve

The next thing we would like to cover as a probable cause of the code P0442 is a defective purge valve in your EVAP system.

Similar to the vent valve, this purge valve also has a solenoid design. This means that they fail in similar ways. They can remain open or closed. If the purge valve remains in an open position, you will have a P0442 code and a problem with the emission system.

This is why you should also bench-test this component with a multimeter.

6. Defective Leak Detection Pump

And the last probable cause of a P0442 code is the EVAP system leak detection pump. This pump is designed to detect vacuum leaks and may occasionally malfunction.

This can cause a problem in the emission system as in our case with code P0442.

Symptoms of Code P0442

Since we have covered the probable causes of the P0442 code and the evaporative emission system leak, we can now move on and cover the symptoms of the EVAP leak.

Knowing the symptoms will help you diagnose the fault much sooner than anticipated and without many problems.

1. Check Engine Light Activated

First on our list of symptoms of code P0442 What we are going to cover is obviously check engine light. But you must remember that this light is not only activated with this code, it is only an indicator that there is a fault, but it does not specify which one.

If activated check engine light you must scan your car to check which code is activated.

2. Gasoline smell

Whenever you have a problem with the EVAP system, you will have this characteristic smell in your car, usually near the fuel tank.

This smell can be annoying to many, and its intensity will depend on the size of the leak you have in your system.

3. Rough idle

If the purge valve is left open, stuck in this position, a large amount of unmetered gases will enter the intake and affect the fuel mixture.

This will be mainly noticed in car idling. It will be irregular and even tend to turn off the engine.

4. Misfire

For the same reason as irregular idling, the car will have ignition problems. There will not be a correct mixture in the chamber, making it difficult to ignite the mixture, or occurring out of place and time.

Of course, this would only happen if the EVAP system leak comes from the purge valve side, and it is considerable.

How to Diagnose and Repair Code P0442?

To diagnose this fault, you must scan your car and check the code that is activated. You may find P0442 alone, or accompanied by other codes, depending on the severity of the fault.

To rule out intermittency in the appearance of the code, it is necessary to erase all the codes with the scanner, and then start the car to perform a test. If after a reasonable time, the code does not appear, it means that there is intermittency.

But if it appears again, you should follow your diagnosis.

The first thing you can do in this case is check your car’s gas cap. Make sure the gas cap is sealing properly and there are no leaks escaping from the fuel tank.

Also, make sure the EVAP system does not leak. Unfortunately, this can be tricky because you will have to use a smoke machine to locate these leaks. Finding these leaks without a smoke machine can be really difficult.

Then the next things to test are the purge valve and the vent valve. Especially the vent valve, which can easily trigger a P0442 code. If you detect the fault in these valves, you can replace them, they are easy to dismantle and are not expensive.

If the problem is not there, you should check the gas tank and see if the fuel pump seal is leaking. If it leaks, you should proceed to replace it. This can also be verified with a smoke machine along with the gas cap.

Common Errors When Diagnosing Code P0442

Don’t ignore other codes that appear with P0442. You may see other EVAP system-related trouble codes simultaneously, such as P0440, P0441, P0443, P0449, P0452, P0453, P0455, and P0456.

Take note of these as they can help you diagnose what triggered P0442. It will help if you don’t assume that the gas cap is causing P0442, although that is the most likely source of the problem.

Perform a full diagnostic to check for other problems before assuming the gas cap is the culprit.

How Serious Is Code P0442?

There is minimal risk of damage to your vehicle with the code P0442. The severity level of this code is low. You should fix the problem before your next inspection, but you can drive safely until you have a chance to repair it.

Tips to Avoid Code P0442

Always make sure to replace the gas cap tightly after filling the tank. If you lose your gas cap, don’t replace it with the first one you find.

If your gas cap doesn’t fit properly, you’ll likely continue to receive EVAP leak trouble codes. You should always get good quality OEM parts. They will be more expensive, but they will be worth it.


You may also be interested in Code P0441. Causes, Symptoms and How to Fix It

Although this fault is not really that serious, you should arrange for a diagnosis and repair as soon as possible, to avoid further damage as the symptoms worsen.

Furthermore, this activated code will not allow you to pass the emissions tests to which you subject the car.

As you may have noticed, to carry out the diagnosis, they will need a smoke machine and connect the system to it. This can be difficult to do in your own garage, so it is best to take it to a specialized workshop.

If you want to know other articles similar to Code P0442. If the evaporative Emissions Control System Leak is Detected you can visit the category Fault Codes.


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