Home Diagnosis and TroubleshootingOBD Diagnostic Error Codes P0455 – A Simple Gas Cap Issue Or Much More Than That?

P0455 – A Simple Gas Cap Issue Or Much More Than That?

by Jordan Harris

Have you got a check engine light and a P0455 error code? Well, if this is the case, then you are at the right place because there will be a lot to cover on this topic where we will dissect this problem into small bits just to deliver you the right information to quickly overcome the issue.

Having a problem like this can be really frustrating sometimes. Especially if you have a check engine light. The light is there on the dashboard constantly notifying you that you have a problem but you just don’t know what is going on with your vehicle.

In this situation, you are stuck guessing the issue and asking yourself what could it be. Is it something serious or is it something really simple? And without the proper troubleshooting skills, you will be highly unlikely to be able to diagnose the problem. This is why you need to familiarize yourself with car diagnostics and learn at least the basics of it.

Meaning that you should know what is computer diagnostics and how it is done the right way, especially for this problem. And you shouldn’t worry because we are going to help you out.

First, we will learn what is diagnostics and how it is performed, and with what tools. Then we will cover the error code P0455. We will learn what this code means and is it serious. Then we will cover the causes for this code, the symptoms, and the diagnostics process. We will also cover what this code means to different manufacturers. So, if you want to learn more about this problem. Please follow along till the end.

P0455 Evaporative Emission System Leak Detected Gross Leak No Flow

Now before we dive into more complex topics and understand more about the P0455 code. Let’s start from the basics and that is how this process is done the right way.

This will be extra useful for beginners who are not familiar with computer diagnostics and want to start learning things. So, if you are a beginner, follow along. If not you can jump to the causes and the representation of this problem in different makes and models.

So, what is diagnostics? As you probably know, all modern vehicles are computerized. It’s not like back in the good old days when you only had to do some tweaks on the carburetor and the valves to maintain the engine work in good condition.

Nowadays there are dozen of different sensors that communicate with the ECM which is the car computer.


Then the ECM evaluates the data that it receives from the sensors and if something doesn’t match it will decide to show the check engine light on the dash.

This check engine light indicates that there is a problem with the vehicle. Like in our case, the error code P0455 indicates that there is a problem with the EVAP system. Before we cover the EVAP system let’s see the tool you will need to diagnose a check engine light.

The special tool you will need for this purpose is an OBD2 scanner tool. This tool will deliver you with the most essential data on how your engine works and what codes your car has if there are any.

This is an essential tool you need when you are running a modern automobile. It will help you diagnose the P0455 code with ease. So, grab one for yourself if you want to wrench on your car.

How EVAP System Works?

Now before we cover the P0455 code, let’s learn more about how the EVAP system works in a car. Knowing this stuff will help you out immensely in diagnosing the problem with your car. Since one thing is to know the code and completely another thing is to understand how everything works together and estimate where is the root of the problem. So, what is an EVAP system?

The EVAP system is a special emission system. This system is designed to collect the fumes that are created in the gas tank from the evaporation of the gasoline.

As you probably know, in the gas tank there are fumes that are released from the gas. So, there was a need for something to be created to collect these fumes in order to avoid them escaping into the atmosphere and polluting the environment. And here the EVAP system comes into play.

This system plays a big role in tackling this problem with the pollutants. The fumes are collected from this system and are driven into something known as a charcoal canister. Then from this charcoal canister, the fumes are driven into the intake manifold and burned in the combustion.

In order for this system to work right, there is a vacuum that has to be created. Meaning that this flow of gas is restricted by something known as a purge valve. This valve tends to break and cause you problems. Namely, the P0455 code or another code with similar meaning.

Don’t get me wrong, there could also be a problem with the charcoal canister or another component in this system as well. But more about that in a bit where we will cover the causes. Now let’s elaborate more on the error P0455.

What Is The P0455 Code?

Now as we covered the EVAP system and we learned what is its role and how it functions. Let’s now learn more about the P0455 code. Let’s cover the basics of this problem before we dive into the causes and symptoms that you will face.

The definition of the code is: P0455 Evaporative Emission System Leak Detected Gross Leak No Flow. And this greatly tells you more about this problem.

It basically means that you have a vacuum leak in your EVAP system. Meaning that something inside doesn’t seal quite well and you have trouble running your car. But this isn’t a very serious problem.

So, you will be able to drive your car for a short amount of time. It will probably not going to affect the performance of the vehicle much. Even though, experiencing symptoms will be quite noticeable. But more on the symptoms and the causes later in this article.

What is important for you is to diagnose the code with an OBD2 scanner tool and learn more about what is causing the issue. But what could be the causes for the P0455 Chevy code? Well, that’s what we are going to cover next.

Causes For P0455 Code

So, what are the possible causes for the P0455 code? Let’s elaborate on them in the following chapters in depth.

Understanding the causes of the P0455 code will help you in fixing the problem much sooner than previously anticipated. So, if you want to learn more about this and how to overcome this problem, follow along.

1. Bad Gas Cap

A simple thing as a bad gas cap can cause this P0455 code on your car. But why is this the case? Well, this is the case because the gas tank should be pressurized.

If the gas tank is not pressurized. Meaning that if there is a leak from the gas cap because this cap doesn’t seal well, then this could cause the check engine light to show on the dashboard and this code along the way.

The first thing you should check when you have a problem like this is the gas cap and if it seals well. If it doesn’t seal, replace it with an OEM cap. An original gas cap is essential because aftermarket ones are also prone to this problem. Now let’s move to the next cause.

2. Bad Purge Valve

A bad purge valve is another very probable cause for this P0455 code. Why is this the case? Well, this is the case because this purge valve basically allows the gases from the fuel tank that are accumulated in the charcoal canister to enter the combustion.

If this valve is stuck closed all the time or stuck open, it will cause a lot of trouble for you. And one of these troubles is this error code or a similar code that indicates a problem with the EVAP system.

And frankly, after the gas cap, this is another very common failure point when it comes to problems like this happening. So, beware of this valve. Now let’s move to the last cause.

3. Vacuum Leak In The EVAP System

And the last probable cause for this problem is connected with the vacuum lines or the charcoal canister. If this system is leaking from somewhere it will develop the P0455 code.

This is a complex system with a lot of piping, so using a smoke machine will probably be needed to find the place where this system leaks.

This happens rarely though but when it does, it is a real pain to get it diagnosed and determine from where the leak comes from. Now let’s move to the symptoms of the P0455 code.

P0455 Symptoms

Now as we understood the main causes for this P0455 code, let’s cover some of the symptoms that you will probably face whenever this problem occurs on your vehicle.

There are rarely big noticeable symptoms. But if you really understand your car and can feel subtle changes, you will notice that something is off. Now let’s cover them in the following chapters.

1. Check Engine Light

The first symptom that you will notice when you are having a P0455 code is the check engine light on the dash. This is kinda logical because if you are already familiar with this error, you have probably are aware of this light.


For those who don’t know, if you have a check engine light, you will have to diagnose it with an OBD2 scanner. And then based on the codes to determine the root of the problem. And frankly, the code readers are giving extra good input on this problem. Later on, we will learn more about this code on different makes and models. Now let’s move to the next symptom.

2. Lean Air To Fuel Mixture

The second very probable symptom if you have the P0455 code is the symptom with the lean air to fuel mixture. But why is this the case?

Well, this is the case because if the purge valve is stuck open means that there will be a lot of unmetered air that enters into the combustion process. And the consequence will be the lean air to fuel mixture. Meaning that there will be too much air and too little fuel.

So, the car computer will notice this and will throw some other codes besides this one that we are discussing where you will see the lean air to fuel mixture warning. Now let’s move to the following symptoms.

3. Increased Fuel Consumption

Another symptom that is often associated with lean air to fuel mixture and the P0455 Dodge is the increased fuel consumption. But why is this the case?

Well, this is the case because this wrong air to fuel mixture will cause the computer to put more fuel into the combustion.


Imagine that your purge valve is broken and unmetered air enters the combustion. Then the computer will say, hey there is too much air and too little fuel. Let’s dump more fuel in the mix. And this will often cause a number of other headaches for you.

Namely, fouled spark plugs, and misfires. But the important thing that will hit your wallet is increased fuel consumption.

That’s why make sure that you notice this symptom on time. This situation will greatly affect your driving and also the performance of the engine and that we are going to cover next.

4. Low Engine Power And Misfires

And the last symptom of the P0455 code that we are going to cover is the low engine power that will be noticeable.

Usually, whenever there is a vacuum leak in the system, you will notice a worsening in performance. And so is the case with this problem. The performance of the car will worsen and you will notice it in the form of engine misfires, low engine power, as well as rough idle. The car will not be happy.

Even though the EVAP system is only an emission system, it could still really hurt your performance, and sorting this problem should be your top priority. And how you can diagnose a P0455 code we are going to explain up next.

Diagnosing The P0455 Code

Now let’s learn how you can diagnose a P0455 code on your car. Diagnosing this problem can be a breeze but it can also be a complete nightmare if there is a leak in the EVAP system at not such an obvious place.

The first place that you need to look at is the gas cap. Remove the gas cap and give it a good cleaning. Also, clean the filler neck. Then try if this has solved the problem.

If it didn’t, then you need to take things further and check the purge valve. First, you need to find this purge valve and this can be rather tricky. Just go online and browse images from your engine plus the phrase “EVAP purge valve” or “purge solenoid” to get the right information.

Then the second thing you will need to do is to bench test it with a multimeter. You just need to set up the multimeter to measure continuity also known as resistance or ohmmeter.

Then place the probes on each contact and see if there is continuity or not. If it beeps it means that the purge valve is good, if there is no sound means that the purge valve is dead.

If you want you can power up the purge valve by applying a positive and a negative. Then with a vacuum tester, you can create a vacuum. In this case, the purge valve should open if its good. If it doesn’t open then it is probably broken.

If the gas cap and the valve are good, then you will need to test the system with a smoke machine to determine from where this leak comes if you want to sort the P0455 Chevy code.

P0455 Code In Different Manufacturers

Now before we conclude our article on the P0455 code, let’s cover what this code means for certain carmakers. Since some cars have a different diagnosis when it comes to this issue.

P0455 Dodge, PO455 Jeep

On some of the ’90s and the early 2000s Dodge, Chrysler, and Jeep models, this P0455 code is very common. The main problem was because they used really cheap hoses that love to crack and develop a ton of vacuum leaks.

This makes the diagnostic process on these engines a real pain to do since these leaks come from all over the place. So, your best bet would be to avoid these old models.

P0455 Nissan

In Nissan models, this P0455 code is caused by a bad vent control valve. This control valve is usually located on the rear of the car where the charcoal canister is located.

In order to fix this problem on your Altima, Versa, Rogue, Pathfinder, or QX4 is to replace this control valve. This is mostly caused by cars produced between 2005 and 2007

P0455 Hyundai

On Hyundai vehicles, this code is mostly caused by the Purge Control Solenoid Valve, which is also known as PCSV.

Replacing it will hopefully sort the issue on your vehicle.

P0455 Chevy Silverado

On the Chevy Silverado, this is a common problem that often happens because of a number of things. Namely a bad vapor canister purge valve, faulty charcoal canister, fuel tank sending unit, bad fuel cap, bad filler neck.

All these different components can attribute to the development of the P0455 Chevy Silverado and you should be aware of them before diagnosing.

Cost To Fix?

The cost to fix the P0455 is relatively cheap. If its the gas cap or the filler neck you will highly likely pay less than $100 to fix this problem.

The purge valve is even cheaper, costing about $50. In addition to this also count the labor which is between $50 and $100 and this could alter the cost of fixing this problem.

Facts about P0455 Code: What you Need to Know

  1. P0455 diagnostic trouble code signals a leak in the Evaporative Emission Control (EVAP) system that cannot maintain pressure.
  2. The EVAP system aims to prevent fuel vapors from escaping into the atmosphere.
  3. The fuel tank, fuel cap, vent valve, purge valve, and the evaporative canister are the five main components of the EVAP system.
  4. The ECM will perform leak tests to make sure that all parts of the EVAP system are working.
  5. The most evident symptom of a P0455 code is a strong gas smell near the fuel tank, besides the check engine light coming on.
  6. The leak causing the P0455 code is most often due to a faulty fuel filler cap or leaks from the EVAP system.
  7. Immediate attention from a qualified technician is required for this diagnostic code since fuel leaks from the tank or any associated seals could cause it to set.
  8. It is still safe to drive with a P0455 code, but it’s best to have it checked immediately if strong fuel odors are present.
  9. Diagnosing a P0455 code requires the use of an OBD-II scanner and completing a full drive cycle test to determine the location of the leak.
  10. Repairing a P0455 code requires various steps, including checking other codes, inspecting the gas cap, performing an EVAP system leak check, and replacing any leaking hoses or seals.


In this article, we have covered quite a bit when it comes to the problem with the P0455 code. First, we learned what this code is and what it represents. We covered the basics of car diagnostics as well as the basics of the EVAP system since this system is most affected by this code.

Then we covered the causes for this problem which were the gas cap, the purge solenoid, or another vacuum leak in the system. And after the causes, we covered the symptoms which include the learn air to fuel mixture, poor engine work, and check engine light.

Lastly, we discussed how you can diagnose and sort out the problem.


Now let’s answer some common questions concerning this problem.

What Is Code P0455

This is a trouble code that your car has. Meaning that your car has a certain problem with the EVAP system and this needs to be further diagnosed so the problem is solved. Your best bet will be to take things further and diagnose the issue as soon as possible. It will not be a big problem at the beginning but the more you wait, the bigger the chance things get worse on your car. That’s why don’t ignore this error code.

What Does Code P0455 Mean

This code means that you have a problem with the EVAP system. This EVAP system is an emission system that collects the fumes that are created in the gas tank and drive them into the intake manifold so they could burn in the combustion process. Avoiding further damage to the environment and keeping our health safe. The error code means that you have a certain problem with this system and this is often connected with the gas tank filler neck or the gas cap. Or in some cases with the purge valve solenoid.

How Do I Fix Code P0455

Fixing this code really depends on the root cause of this problem. Whether this problem is caused by the purge valve, gas cap, filler neck or there is another vacuum leak in the EVAP system. These types of leaks are often diagnosed with a smoke machine.

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