P0440 – A Simple Problem With The EVAP Or Much More?

by Conner Mckay

Are you having a check engine light and the code P0440 has shown up on the diagnostic tool? If that is the case, then you are at the right place because there will be a lot to cover on this topic where we will learn everything when it comes to this topic.

Having a problem like this can be a really frustrating thing to deal with, namely because the car can start to develop symptoms and also ruin your driving performance. Whenever there is a code on the cluster, it can only mean one thing. And that is a problem that needs to be diagnosed and fixed.

What is important for you is not to ignore these symptoms and act accordingly. By this, I mean that you need to act quickly and avoid further problems that could be attributed to this issue. As you probably know, everything in the car is connected. And when one component fails, it greatly affects the others as well. So, everything has to be in proper working order if you don’t want to deal with further issues. And we are going to help you out with that.

First, we will cover what is car diagnostics in general and introduce you to the problem of the P0440 code. Then we will cover the causes of why it happens as well as the symptoms that you might be experiencing when dealing with this issue. Later on, we will learn how you can diagnose and fix the problem. And normally, at what cost will that be possible. So, if you want to learn more, follow along.

Introduction To Car Diagnostics

Now before we dive into the P0440 code, let’s first introduce ourselves to car diagnostics. Since you are familiar with this code you probably know how it is done. But there are people that are reading this who are not into cars and want to start learning.

And there is nothing better than starting with the basics. If you feel like you have the grasp of the knowledge needed, you can jump to the causes and symptoms. If not, keep up with us for a bit.

Nevertheless, car diagnostics is real science. It’s the same as you being a doctor. But a doctor for cars. And as any doctor out there, you need your stethoscope and other equipment to perform these duties. Which in this case are the OBD2 scanner and the multimeter tool.

As you probably assume, cars nowadays are all computerized. It is not like back in the days when you just tweaked the carburetor a bit and call it a day. Modern vehicles require a modern approach.

There are a ton of different sensors in each car. And these sensors communicate with something known as ECU (engine control unit). Some carmakers call it ECM, some call it PCM. But in simple words, this is the engine control unit also known as the car computer.

The car computer basically is the brain. And you use the OBD2 scanner tool to get access to this component and see what kind of trouble codes are you having on your vehicle. Without this, you will never be able to tell if you have a P0440 Toyota code.

If you fix a car without this information, it is the same situation as you are doing surgery blindfolded. So, let’s elaborate more on this code and learn more about it.

P0440 Evaporative Emission System

Now let’s say that you performed your diagnostics and you determined that the car has a P0440 trouble code. What this code means and how you can overcome it? Let’s elaborate.

The explanation for this code is P0440 evaporative emission system malfunction. Meaning that there is a problem with the EVAP system on your car.

If you don’t know what the EVAP system is don’t worry, we are going to explain it in the following chapter in depth where we will cover more about this system and how it works.

The important thing for you is that this code is not that big of a deal. Like with any trouble code, you should know about it and sort it out in order to get the check engine light out of your way. But you shouldn’t panic because this problem can wait for a bit. But what is the reason behind this code?

Well, there could be more than a few things honestly. But the options are only limited to components of your EVAP system. Meaning that this code cannot be caused by anything else than the EVAP system and there you should look for your problem.

But to get there, you still need to understand how this system works in practice. Knowing how this stuff works will save you a ton of money in the process and will make your diagnosing process a breeze. Now let’s learn how this system works in the following chapter.

How Does The EVAP System Work?

Now as we cleared what the P0440 trouble code means and we determined that there is a fault with the EVAP system on your car. Let’s now learn what is this EVAP system in the first place? What does that EVAP acronym even mean? Let’s explain.

The EVAP acronym stands for Evaporative Emission Control System. This system is crucial when it comes to handling the emissions of your car. Without it, our cars would pollute a lot more than they are polluting right now and is basically a total lifesaver. But how does it works?

Well, it is quite simple to explain. There are fumes that are created in your fuel tank from the fuel that constantly is evaporating. And the sole goal of this system is to drive these gases into the engine intake and burn them into the combustion process.

There are a few components of this system. The charcoal canister, the vacuum lines, and the purge valve that opens and closes under pressure.

The fumes first go into the charcoal canister. Then from the charcoal canister, they travel to the front of the car, and there when there is enough pressure buildup, the EVAP purge solenoid opens and allows the fumes to enter the intake.

Then the fumes will burn and will basically get destroyed. The end result will be a car that pollutes less. But what bout the P0440 Toyota code, what could cause this code to appear and ruin your day? Let’s explain more about the causes in the following chapters.

Causes For P0440 Code Occurring

Now as we cleared out how the EVAP system works in practice and how it can cause the P0440 Chevy code, let’s now learn more about the components in this system that can cause this code to occur.

As you probably know, there are a few components in this system and all of them when they fail are starting to show some symptoms like the P0440 trouble code. But which are these components? Let’s find out next.

1. Loose Gas Cap Or Filler Neck

The most basic reason for the P0440 Chevy code to pop up is a simple problem with the gas cap of the car.

If you didn’t know, gas tanks are pressurized. Meaning that there should be no unmetered air entering the gas tank. Everything needs to be up to spec.


And what happens, in this case, is a situation when the gas cap doesn’t seal, or there is a problem with the filler neck that allows the gas tank not being able to get pressurized.

This will confuse the EVAP system and will decide to show the check engine light on the dashboard. Whenever you try to solve a problem like this, you should move from this component and replace it if necessary. Now let’s move to the next probable cause.

2. Bad Charcoal Canister

Another probable cause for the P0440 code is a problem with the charcoal canister. The canister serves the purpose to catch some of these fumes before they are driven into the intake of the car.

Whenever this canister doesn’t work well and gets clogged. It will create problems and will prevent the EVAP system from working correctly. In most cases when this component is the problem, replacement of the canister is an essential thing to deal with.

If you do not replace it. You will never fix this issue. But more on that later on in the article. Let’s finish the rest of the symptoms.

3. Bad Purge Valve Solenoid

Another highly likely suspect for the P0440 code is the purge valve solenoid. This solenoid is opening and closing the gas flow from the charcoal canister into the engine.

It works with the help of a vacuum. When there is a lot of vacuum pressure it opens and when there isn’t it closes.

So, when it fails it basically either prevents the flow of gas into the intake or the solenoid is stuck open and the gas flows into the intake unobstructed.

This could create problems. Namely, lean fuel to air mixture that could cause a ton of problems on the spark plugs and other sensors. This is why this solenoid is really crucial and has to be replaced if it’s faulty. Now let’s move on to the next cause for the P0440 Chevy trouble code.

4. Vacuum Hose Leak

And the last probable cause for this problem with the P0440 code is an issue with the vacuum hoses. As you probably assume, the EVAP system has a ton of hoses.

These hoses are made out of rubber material. This rubber gets old and stiffens up. It will eventually crack because there is pressure buildup in the hoses.

So, this is one of the possible scenarios. Some vehicles are quite notorious for these problems. Mainly because they implement low-quality hoses for this job and they crack extremely easily.

Locating a leak from a vacuum hose can be a real pain. But later on in the article, we are going to explain how it is done. Now let’s cover some of the symptoms that you will experience when there is a P0440 Chevy.

Symptoms Of P0440

Now as we cleared the causes for this problem with the code P0440 out of our way. Let’s now cover the symptoms and learn more about what you could expect this problem to look like in reality.

Knowing the symptoms will help you quite a lot when it comes to diagnosing and sorting out the problem. More on the diagnostics later on, after we discuss the symptoms that this trouble code produces.

It is worth noting that there are no critical symptoms. Some of these symptoms are very mild and will not affect you much while you drive your car. So, what are they? Let’s find out.

1. Check Engine Light

The first and most obvious symptom concerning this problem is the check engine light on the cluster. Without the check engine light, you will not have the right input on what could be wrong in the first place.

So, if you diagnosed the problem and got the P0440 code, you are on the right path to fixing the issue. If not, please diagnose the problem and see if there is an indication of a code like the P0440.


If there is, then you should move on to diagnosing the problem even deeper and finding the right cause for this condition. But more on the diagnostic process, we are going to cover later in this article after we finish the symptoms.

2. Engine Misfires

The second symptom that you will notice when you have a P0440 code is the engine misfires. Whenever there are problems with the EVAP system, then for sure is going to be a lot of unmetered air that will go inside of the engine intake if the purge valve of this system is malfunctioning.

Random misfires will be present. Especially when the car starts and the engine gets warmed up. You don’t want to ignore these symptoms. Mainly because misfires could also ruin other components inside of the engine.

Namely, the problem will take a toll on the spark plugs, O2 sensor, catalytic converter, etc. All, these components are affected when you have a problem like in our case. This is why diagnosing it is key.

3. Fuel Vapor Smell Into The Cabin

Another very common symptom that you will notice whenever you get a P0440 Chevy code is the situation when there is fuel vapor inside of the cabin.

Especially after you pour fuel into the tank. This will be most noticeable in this situation. So, why is this the case?

Well, since the fuel is pouring into the tank, there is evaporation from the fuel and then this evaporation is felt.


But here lies the problem, you close the gas cap and this smell continues to bother you. Here lies the problem. And the problem is caused by a bad gas cap or problem with the filler neck of the car.

This will make the fuel tank not get pressurized and will cause you to see the check engine light, the code P0440 Chevy as well as making you look online and how to solve this problem. But how you can solve this issue? Let’s find out in the following chapter.

How To Diagnose & Fix The Problem With P0440?

So, how you can diagnose the code P0440 code on your car? What is sad in this situation is that this code doesn’t tell you quite a lot about the issue itself.

You know where to look, but you don’t know where to look precisely. This is why it is useful to read some of the other codes if there are any and see if they are connected with the EVAP system.

If there are not any codes out there that indicate a problem with the EVAP system, then you can move on to troubleshooting the components of it one by one.

First thing first, make sure that you inspect the gas cap. You just need to make sure that it seals well. If there is a problem with this component, you will have to replace it with the right OEM gas cap. You can harvest one from a junkyard. Or you can get one from the local parts store. They are relatively inexpensive components.

Then if this doesn’t solve your problem, you might want to look at the EVAP purge solenoid. You can test this solenoid by using a multimeter and a vacuum tester. But you can just go and purchase one. They are also relatively inexpensive.

If the problem is solved after replacing this component, then excellent. If it persists, then you need to inspect the vacuum leaks and the charcoal canister if it’s clogged. You can only do these things by using a smoke machine.

Since these vacuum leaks are really hard to track. Overall, that’s everything you need to know when fixing this P0440 Toyota code. Now let’s discuss the costs involved in this work.

Cost To Fix The P0440 Code

So, what is the cost to fix the P0440 code? This really depends on what is the cause of this problem. But I can tell you that it is not that expensive to sort this problem out.

In most situations, there is a problem with the gas cap or the purge valve solenoid. Both of these components can be purchased for under $50 and replaced easily. The charcoal canister on the other hand is more expensive and could cost between $150 and $500 but this component rarely fails.

Finding vacuum leaks on the other hand can be troublesome and you will have to get yourself a smoke machine. This is why it is rather convenient to take the car to a shop and they will sort out the problem for about $200 to $400.

P0440 Chevy

The P0440 Chevy code is a trouble code that appears on Chevrolet and other GM vehicles. It indicates that there is some problem with the EVAP system of the car.

This code is often caused by a loose gas cap or possibly a bad purge valve. But in some more extreme cases, it could be caused by other things like a charcoal canister or leaks from the vacuum lines.

Whenever you have a problem like this on your Chevy. It is worth checking out your gas cap first and then moving on to other possibilities.

P0440 Toyota Camry

The P0440 Toyota Camry is quite common to occur. Every Camry owner once in its ownership had an issue with this trouble code.

As we already explained, this code is often caused by a bad EVAP system or problems with the gas cap. But on Camrys, this usually is caused by a bad purge valve solenoid that is part of the EVAP system on your Camry. Just replace this valve and you will be good to go. No more problems.

Facts about P0440 Error Code and EVAP System:

  1. P0440 is a generic OBD II code that indicates a malfunction with a vehicle’s EVAP system.
  2. The third numeral in the code sequence signifies where the vehicle’s onboard diagnostic system has encountered an error.
  3. The number 4 in P0440 indicates a problem with the vehicle’s auxiliary emission controls.
  4. The two immediate symptoms of the P0440 code are the illumination of a vehicle’s check engine light and a fuel vapor odor around the vehicle.
  5. A malfunctioning fuel tank vapor system or vapor pressure sensor could result in a P0440 code.
  6. Common causes of a P0440 code include sealed fuel tank vapor lines, a loose gas cap, and leaking fuel vapor system components.
  7. Vapor leaks in the fuel vapor system can be very dangerous and can cause a failed emissions test.
  8. A mechanic with advanced testing tools is required to accurately diagnose the problem and inspect the EVAP system.
  9. A smoke leakage test is important to locate the cause of the vapor leak.
  10. Repairing a P0440 error code may be as simple as securing or replacing the gas cap or require repairing or replacing leaking vapor system components like a vapor control valve or carbon canister.


In this article, we have covered quite a bit when it comes to the P0440 code that has started troubling you. First, we covered the basics of what is car diagnostics and we elaborated more about this trouble code. We learned that this is caused by the EVAP system.

Then we have covered the symptoms that are often happening when this code is appearing. After we learned how to diagnose and fix the problem. And at what cost is this possible.


Now let’s answer some frequently asked questions.

What Is The EVAP System

The EVAP system is an evaporative emission control system. This system is designed to catch the fumes created in the gas tank and bring them into the intake and burn them in the combustion process. It is basically an emission system that is designed to reduce the emissions of your vehicle.

What Does The Code P0440 Mean

This code basically means that there is a problem with the EVAP system on your vehicle. Some of the components are faulty. Starting from the gas cap that can get loose over time and let the gas tank breathe. Which shouldn’t be the case, or possibly there is a problem with the EVAP purge solenoid, charcoal canister, or the vacuum lines.

How Do I Fix Code P0440

Fixing the code really depends on the cause of the problem. If it’s a simple gas cap, then replacing the gas cap will sort out the issue. If the problem is the purge valve solenoid then you will have to replace this component. First, diagnose the problem and then fix the issue if you want to achieve a good result.

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