P0442 Code – A Simple Gas Cap Issue Or Something Else?

P0442 Code – A Simple Gas Cap Issue Or Something Else?

Have you got a check engine light? You went through the diagnostics and you got the P0442 code? Well, if that is the case, then you are at the right place because there will be a lot to cover when it comes to this error and how to sort it out.

Having a problem like this can be really frustrating to deal with. Especially the P0442. Why I’m saying this? Well, because it is true. These vacuum leaks are a real pain to find and diagnose the right way. You could spend hours and hours looking for them in vain.

That’s why you need to step up your game and learn how to diagnose problems the right way. And by this, we mean using some ingenuity and understanding of how everything works in your car. You need to know how everything is routed. So, you have a clear understanding of where to look for your problem. And precisely like in a case like this where finding the problem could be a real pain. But we are going to help you out.

First, we will cover the basics of car diagnostics and what you will need for this type of work. Then we will learn how the EVAP system works and how everything is connected. After this, we will cover the causes of the P0442 code as well as the symptoms that you will notice when you have a code like this. In addition to this, we will understand how you can diagnose and sort out this problem quickly and effectively. So, let’s begin.

Introduction To Car Diagnostics

Now before we dive into more complex topics and start explaining the P0442 code, let’s first learn more about the basics of car diagnostics. I bet that there are people who are reading this and are not quite familiar with car diagnostics and how it is done the right way and the tools needed.

What is important when it comes to car diagnostics is to know that things are not like they were back in the day. Back in the day, everything was easy and diagnostics were based on the opinion of the mechanic about what could be wrong. And this required a lot of experience.

Nowadays, everything is connected to a computer. Also known as ECM or PCM as some manufacturers call it. This computer is basically the brain of the car and this computer works on a map. Or a program let’s say.

It has all the factory-recommended settings on it and whenever this computer that something doesn’t quite match with the factory-recommended settings. It will decide to throw at you the check engine light.

This light is really confusing because it doesn’t tell you anything about the problem. You could only guess what could be wrong with the car.

In order to access the computer, you will need a special device. Also known as an OBD2 scanner. With this tool, you will be able to access the OBD2 port that each modern car has. And then you can check what error codes you are getting.

If this is the case like in this article and you get the P0442 code, then you probably have a problem with the EVAP system. But what is this system and how does it work? Well, that’s what we are going to learn next.

How Does The EVAP System Work?

Now before we cover the causes and the symptoms of the P0442 code, let’s first cover how this EVAP system works in general. What this system is and what is its role in the automobile?

The EVAP is an abbreviation of the phrase Evaporative Emission Control System. So, now you get the point that this is a special emissions system that is equipped on our cars. But what does this EVAP system do in the car?

Well, this system has a special role. And that role is to collect all the fumes that are inside of the gas tank and redirect them into the intake manifold and then into the combustion process.

This means that this system stretches from the rear where the fuel tank is located, up until the front end of the car where the intake is. But why all this effort?

Well, this effort is needed to maximize the reduction of emissions. As you know fuel evaporates and the fuel tank needs to be pressurized if you want to avoid these fumes to escape into the atmosphere and pollute.

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

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

But sometimes things don’t work as they should and unfortunately the system malfunctions. So, you will highly likely get a check engine light and the P0442 code on the cluster. But what does this code means? Let’s elaborate more on that next.

Evaporative Emission System Leak

Now as we learned how the EVAP system works in practice, let’s focus on the problem And that is the P0442 code and its meaning. What does this code mean and what is its definition?

The definition for this code is “Evaporative Emission System Leak” or “Evaporative Emission Control System Leak Detected”. But what does this means?

Well, this means that you have a vacuum leak in your EVAP system. Something isn’t sealing well in this system and the PCM has detected this issue. Then after a thorough analysis of the data determined that this problem keeps repeating over and over. So, it decided to show the check engine light.

Then based on this check engine light you probably came here to see what could be the cause for this P0442 code appearing in the system. You are probably worried because of this but should you be worried?

The answer to this question is no. Even though there is a check engine light on the cluster. It doesn’t mean that you should get alerted scratch your head all day what could it be. It’s just a small leak.

What is useful for you to know are the causes of why this leak appeared in the first place. To know what could cause this problem with the P0442 code and move on from there. In the following chapter, we are going to cover precisely where we will cover all of the causes of this situation.

Then after that, we will go through the symptoms, and in the end, we will learn how to diagnose and sort out the problem quickly and effectively. So, follow along.

Causes For The P0442 Code

Now as we covered the basics of car diagnostics and the problem with the P0442 code, we can now move on to the probable causes of this problem.

Knowing the causes will be extremely useful for you as an owner because you will know where to look and quickly uncover this problem. This is why you need to follow us carefully until we cover every possibility out there for this issue. Now let’s begin.

1. Bad Or Loose Gas Cap

One of the simplest things that could trigger a check engine light and P0442 code is the gas cap. Even on some gas caps, you have the warning that you need to tighten them up if you want to avoid a check engine light.

So, the first thing that you would want to look at is this gas cap. You know where it is, just make sure that is nice and tight. Then clear off the codes and cross your fingers.


If the code still appears, it could be because you have a faulty gas cap or a faulty filler neck. The best is to clean them off from the debris and try again. If else, you can just go ahead and replace it with a new OEM gas cap. This will hopefully solve the problem with the P0442 code. If not, move on to the next possibility.

2. Bad Fuel Pump O-Ring Seal

The next possibility that we would like to cover is the fuel pump. More precisely the seal that sits between the fuel pump and the fuel tank.

This seal needs to seal 100% and allow no fumes to escape into the atmosphere. If this seal doesn’t do its job the right way. You could have vacuum leaks and a check engine light with the P0442 code or any other code connected to the EVAP system.

So, it is often advised for you to check this seal if you think that everything else is sealed well. Sometimes even small things like this can ruin your driving experience. Replace the seal if you suspect it. At least these seals are really cheap and can be purchased for a few dollars.

3. Leak In The EVAP Hoses

The third very common cause for the P0442 code is the leak found in the EVAP system hoses. All these hoses are made out of cheap rubber and as rubber ages, it starts to deteriorate and this deterioration will cause the rubber to get hard and crack.

It’s not like back in the good old days when everything was made out of quality metal components. In this EVAP system, everything is either plastic or rubber.

And some manufacturers that use some of the cheapest things that can get, will also cause a lot of headaches to owners. So, we can say that some cars are notorious for developing a P0442 code by nature. This is why you need to do proper research before you go out there and purchase a car. This is why you won’t be dealing with things like this in the future. Now let’s move on to the next probable cause.

4. Bad EVAP Vent Valve

The next thing that we would like to cover as a cause for the P0442 code is the bad EVAP vent valve. This vent valve works along with the purge valve.

But unlike the purge valve that purges the system, the vent valve vents the system. Meaning that it allows air to flow into and out of the charcoal canister.

This valve as well as the purge valve works with the help of a vacuum and this unit is basically a solenoid. Meaning that it is a closed circuit. Whenever it fails it could cause you a check engine light and P0442 code or another code connected more precisely to this component.

So, whenever you have the P0442 code and you have an emissions system problem, it is worth giving this component a test with a multimeter and seeing if it works or not. Now let’s move on to the next probable cause.

5. Bad EVAP Purge Valve

The next thing that we would like to cover as a probable cause for the P0442 or P0441 code is a bad purge valve in your EVAP system.

Similar to the vent valve, this purge valve is also a solenoid design. This means that they fail in a similar fashion. They can stay open and closed. If the purge valve stays in an open position, you will have a P0442 code and emission system problem. That’s why you will also need to bench test this component with a multimeter in the process as well.

Or just replace it altogether, it is not more expensive than $30. So, sometimes it is more convenient to replace these components than to test them.

6. Bad Leak Detection Pump

And the last probable cause for a P0442 code is the leak detection pump of the EVAP system. This pump is designed to detect vacuum leaks and sometimes it can malfunction. Causing you an emission system problem like in our case with the P0442 code.

EVAP Leak Symptoms

As we have covered the probable causes for the P0442 code and the evaporative emission system leak, now we can move on and cover the EVAP leak symptoms. Knowing the symptoms will help you diagnose the problem much sooner than previously anticipated and without a lot of trouble. So, let’s cover the symptoms briefly in the following chapters.

1. Check Engine Light And P0442 Code

The first in our list of EVAP leak symptoms that we are going to cover is obviously the check engine light. And you probably are aware of this situation since you have diagnosed this problem with your car.

But what is also worth noting is the other different codes that you will get whenever you have a problem like this with the EVAP system.


A lot of these issues come together. So, don’t be surprised if you experience a P0440 or a P0443 code as well. All these codes that start with 44 are somewhat connected to this EVAP system and can mean that you have an evaporative emission system leak. Now let’s move on to the next probable symptom.

2. Odor Of Gas Fumes

The second most common in our list of EVAP leak symptoms that can cause the P0442 code or a similar one is a situation with gas fumes. These fumes will be really present whenever you have a problem with this EVAP system.

This is the same smell that often occurs when you are at the gas station while pouring fuel into the car. But in this situation, this smell will be present inside the cabin because the EVAP is leaking.

That’s why you need to address the problem as soon as possible and make sure that these fumes are no longer present in the cabin.

3. Rough Idle And Misfires

And the last of the EVAP leak symptoms that we are going to discuss that is associated with the P0442 code is the rough engine idle and frequent misfires.

This symptom often occurs if the purge valve is not closing and is open all of the time. This will result in a lot of unmetered air entering the combustion and then cause the car to run poorly and misfire really often.

So, if you notice some codes like the P0171 or possibly P0174, don’t be surprised. Because you could be running lean because of these EVAP leaks that often occur on cars and cause these emissions system problems. But how you can diagnose a problem like this? Well, that’s what we are going to cover in the next chapter.

How To Diagnose And Fix P0442 Code?

Now let’s see how you can diagnose a P0442 code. What you could do when it comes to diagnosing and sorting out this problem quickly and effectively?

The first thing you can do in this case is to check the gas cap on your car. Make sure that the gas cap is sealing the right way and that there are no leaks that are escaping from the fuel tank.

Also, make sure that the EVAP system is not leaking. This unfortunately can be tricky because you will have to use a smoke machine in order to locate these leaks. Finding these leaks without a smoke machine can be really difficult.

Then the next things you want to test are the purge valve and the vent valve. Especially the vent valve can trigger a P0442 code. You can also replace them since they are not really expensive and this could be done fairly easily.

Then if the problem still persists, you need to check the gas tank and see if the seal of the fuel pump is not leaking. If it’s leaking then you would probably need to replace it. This can also be checked with a smoke machine in pair with the gas cap.

In the video above, you can check how this process of diagnosing and fixing the problem with the P0443 code is done the right way. If you don’t want to struggle with this, just visit a shop that has a smoke machine and let them test your system. But how much it will cost you?

Cost To Fix This P0442 Code

So, what is the cost to fix this problem with the P0442 code and seal this small leak in your EVAP system? Well, the answer to this really depends much on the actual cause of the problem.

The diagnostics itself can cost you between $200 to $300, just to find this small leak. Then the repair will also cost you probably between $120 and $250. Depending much on the work and the parts involved in this job.


Still, you can try to fix it on your own by replacing some components like the valves or the gas cap. But when it comes to a P0442. The problem often lies in the piping of the EVAP system or possibly in the fuel tank seal.

Facts on P0442 Code: Understanding EVAP System Leaks

  1. P0442 is an OBD-II code that indicates an evaporative emission control (EVAP) system leak.
  2. P0442 is not a serious issue for short-term drivability but can lead to high fuel consumption if neglected.
  3. The EVAP system is installed in a car to keep fuel vapors from escaping into the air.
  4. The EVAP system uses a charcoal canister to store fuel vapors and two control valves to regulate the flow of vapors.
  5. The ECM performs a leak test to check that the evaporative emission control system is operational.
  6. The causes of P0442 can include a damaged gas cap, EVAP hose leak, charcoal canister leakage, fuel tank leakage, and defective valves or pump.
  7. Drivers may notice an unusual fuel odor and a drop in fuel economy if there is an issue with the EVAP system.
  8. The cost of fixing the P0442 error depends on which part needs to be fixed and can range from $10 to $600.
  9. It is possible to diagnose and repair P0442 at home if you have basic to intermediate knowledge about car mechanics.
  10. Possible DIY solutions to fix P0442 include replacing the gas cap, inspecting the EVAP system for holes or cracks, and performing a smoke test or EVAP leak test.


In this article, we covered quite a lot when it comes to the P0442 code. We learned how the EVAP system works and what role it has.

Then we learned what are the possible causes of this problem and also the symptoms that are often connected to this issue. Lastly, we learned how to diagnose and fix the problem and also at what cost would this be possible.


Now let’s answer some frequently asked questions.

What Does Check Emission System Mean

This means that you have a problem with the EVAP system. This system is an emissions system that most cars have. The reason behind this problem is that you highly likely are having a vacuum leak somewhere in this system.

How Do You Fix Evaporative Emission System Leak Detected

The repair really depends on the problem itself. Sometimes the problem could be a simple gas cap. Sometimes the issue can be a lot bigger like a cracked vacuum hose or possibly a faulty purge or vent valve. Anything is possible.

What Does Code P0442 Mean

It means that you have a small leak in your EVAP system. More precisely that either the fuel tank or the EVAP system is losing vacuum at some point. Deep troubleshooting needs to be done in order to learn the exact cause of the problem. The first thing you need to do is to check the gas cap and see if it seals well.

How To Clear P0442 Code

To clear the code you will need an OBD2 scanner. Just delete all the codes and you will be good to go. If you don’t have a scanner, you can try disconnecting the positive terminal and resetting the computer.

How Do I Fix P0442 Code

Fixing the problem really depends much on the cause of the leak. It could be a vacuum hose, valve, bad gas cap, or something different.

leave your comment

Your email address will not be published. Required fields are marked *