What is a P0455 OBDII Code?

What is a P0455 OBDII Code?

P0455 OBDII Code

No one likes to see a warning light turn on in your vehicle. If you’re like most people, you just drive around hoping that a bump in the road or some other issue caused this light to come on by accident.

A warning light may mean a trip to the shop is needed or you should stop the car immediately. More than anything, it’s probably going to mean you’re going to be spending some money.

For those of you out there that have an OBDII reader, you can check out what the exact issue is with little hassle. Make sure you just have it plugged into the right spot and you’re ready to go.

If you see the following code, P0455 come up, that means you’ve got a serious problem. We don’t mean to be the bringers of bad news, but it’s time to get this checked out.

It means that there is a large leak in the evaporative emissions system because of the evaporation of your gasoline from the liquid phase to the gas phase.

These evaporative emissions systems are designed to catch and store gasoline from the fuel tank or fuel lines that has evaporated. Usually, this isn’t an issue as the fuel is typically collected and reused. But if not, then that’s a big issue.

How can you measure this?

The “easiest” way is to leave an automobile in a contained area for a certain amount of time and then measure the hydrocarbons that have disappeared by evaporation in your fuel system. It’s normal for a little bit to evaporate, but if a certain limit is exceeded then you’re going to see one of those horrible check engine lights come on in your vehicle.

And that’s just the worst.


Symptoms of  A P0455 Issue

So, what are the symptoms of this issue?

If you see this warning signal come on, you might start thinking that there is a ton of gas that is going to evaporate. That means there is going to be a foul smell surrounding your car and it will slowly seep its way into your clothes and vehicle interior.

While that’s possible, many times the smell isn’t very noticeable. The amount leaking out is still pretty small and you may not notice everything.

There are a few reasons for this which we can thank the law of physics for. Gasoline will evaporate at a higher level with greater temperatures, so you might notice that smelly smell when the mercury starts trending upwards. That means that the opposite is true and if it’s cold outside, you may not notice the smell at all.

If you’ve parked your car in your garage or outside and smell gas, do a quick check and make sure there aren’t any open gas containers lying around.

You might also notice a big uptick in your fuel consumption, as this tends to be another symptom. Many times though, it will not be very significant so you will have to monitor your fuel consumption with a fine-tuned comb.


Primary Causes

As we covered above, the P0445 error code tends to be caused by some type of leak in your evaporative emissions system. Just how much of a leak it is can depend on a large number of things.

There can be a lot of car parts that cause these issues. Most notably, it might be the fuel cap being screwed on too loosely. It could also be the filler neck or evaporative system having a leak. Or, it could be the carbon canister, evaporative vent valve, or evaporative purge valve. There are many different options here and one of the main reasons why this error code can be so darn frustrating.

If there is any significant damage to these components, it could lead to the P0455 code or even the P0442 code.

While the code is meant to indicate a leak, it could also mean that one of the components is simply damaged or failing. This could contribute to why you don’t notice a strong smell of gasoline or notice a big drop in fuel consumption.

Diagnostic runs can be made by creating a vacuum within the EVAP system and then subsequently checking for any pressure decay. You could run into and see any potential problems with the evaporative purge valve. It could also be because of the fuel pressure sensor which is responsible for setting off the error code.


How Can You Fix It?

The easiest way to fix this problem is by simply selling your car and buying another one. That way, you won’t have to worry about this particular issue and you can move on from it on a permanent basis.

We jest, because there are plenty of ways you can go about fixing or investigating this issue.

But we have to say ahead of time that it largely depends on the root issue. Some of these can be fixed at home but other times, you will have to take it into a professional.

If the main cause is a leak, then it’s going to be much more obvious and more than likely an easier issue to fix.

The first step you should take is to make sure that the fuel cap is installed. If it’s properly installed, make sure there is no damage or any cuts in the o-ring. If you see any cuts there, then you should go ahead and purchase a new fuel cap.

A quick pro-tip: instead of contacting the car manufacturer for a new fuel cap, head to your local junkyard. It’s going to be much cheaper and looking through junkyards can always be fun.

Replacing the cap, while enough, may take several days to properly clear away the code. So give it a few days before you decide to try and look for another solution. Many mechanics note that this is the most common cause of the failure code.

It can happen to the best of us, leaving your gas cap on top of your car while going about refilling is an easy mistake to make.

If this doesn’t fix the issue, then you’ll have to use a diagnostic tool. If you have seen the OBDII code before, then you probably already have the accompanying scanner.

An evaporative emissions check can only be performed in very specific conditions and if the problem persists, then it make take over a week for it to reappear.

If after all of this you’re still seeing the failure code, you should be inspecting all components of your evaporative system. Go carefully over them in order to check for any leaks. It may help to go over them a few times, as proper angles may be tough to get while checking everything out.

One thing that can help this kind of inspection is by using a smoke test. These smoke tests can usually be done in your garage, but you’re going to need some tools in order to go all DIY on it. We recommend watching a few videos on YouTube to get your head around the basics. The smoke test will push smoke through your system to see if it detects any leaks.

If the smoke test doesn’t work and you can’t notice any issues, then you will have to check that the vent and purge valves. You want to make sure that these components are working in their right state. You’ll also want to monitor the pressure sensor that’s coming from the fuel tank for any unusual readings.

Lastly, if you can’t find any issues you should take it to your local mechanic. They will be able to pinpoint the exact issues and help you locate the problem. It may also be useful if you don’t want to try the smoke test on your own, as all shops will have one ready to use.

One option that mechanics have that you may not have at home is the vacuum tool. This vacuum tool will block one part of the system at a time such as the fuel tank, charcoal canister, and EVAP lines sections. With this method, they’ll be able to check for any leaks and if there are leaks, check for the leak rate.

The only downside to this option is that is can be quite time-consuming and not all mechanics offer such a solution. Be sure and scope around in your area or read online reviews to find if people have taken their cars to certain places for such an issue.



This is an annoying issue that can take time to resolve. Hopefully, it is a simple fix such as a missing or broken fuel cap. As mentioned earlier, you can quickly head to a junkyard or even scope around on Amazon to find the item that will work with your car.

Minor leaks aren’t usually a big deal and while you should definitely be checking out this code, it isn’t something to freak out about if you see it come up. Just go through the steps outlined above to see what the root cause is and do what you can to fix it.

The biggest thing we can stress with this issue is patience. We know you want to get rid of that check engine light as soon as humanly possible, but even some of the fixes that we recommend and have tried ourselves can take up to a week to show positive results.

But, if you are noticing a strong odor from your vehicle (without any other gas containers present), then you should be more concerned. A strong leak can mean a whole host of other issues, including damage to your vehicle and a major loss of fuel consumption.

Also, if you’re not comfortable checking out these issues by yourself don’t try to force it and be sure to have it looked at by a professional. You don’t want to make the situation worse by any stretch of the imagination.

So, while we hope you never have to run into this issue, at least you will be prepared for what could possibly be ahead. Remember to be patient, be thorough, and take it to a professional if you continue to be stumped by that annoying check engine light.


Bryce Newell is an automotive enthusiast who loves to write about the latest news, products, and DIY projects. While Bryce is an amateur in the field, he is passionate about cars and has been since he spent weekends in the garage helping his dad rebuild a 68 Dodge Charger as a kid.

Leave a Reply

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