P0456 Code: How To Fix EVAP System Leak Detected (2024)

Getting an illuminated check engine light while driving is one of the worst things any driver can experience. If it is not followed by any symptoms, that adds to the mystery of the situation. To check for errors that can trigger a check engine light, you can use an OBD-II diagnostic scanner. If after scanning you get a P0456 code, you need to know what you are dealing with.

The P0456 code points to a small leak in the evaporative emissions (EVAP) system. The EVAP system is crucial for lowering the levels of dangerous emissions that the vehicle produces. It keeps the fuel vapors in the EVAP canister while the engine is not running. If there is a small fuel vapor leak anywhere in the EVAP system, that can trigger a P0456 code.

The common reason for any leak in the EVAP system is a problem with one or several parts of that system. Also, sometimes the culprit can be found in the fuel system. Thankfully, this is not a very dangerous error, but it still needs to be resolved as soon as possible. To learn all about the symptoms, causes, diagnostics, and fixes, stay with us.

The Ins and Outs of the P0456 OBD2 Code

What is the P0456 Code?

The P0456 fault code points to an issue with a small leak in the EVAP system. It can be caused by several faulty components, like the charcoal canister, the EVAP hoses, and lines, or the EVAP vent valve. A small EVAP leak can be a result of a faulty or loose fuel cap.

Why does the P0456 Code Appear in your OBD-II Scanner?

The work of almost every component in the vehicle is regularly checked. In the case of the EVAP system, the leak detection pump is always checking for any leaks in the system. If it detects a leak, it notifies the electronic control module (ECM).

In case of a smaller leak, the ECM then triggers the P0456 code. That code is a signal that a small EVAP leak has been detected. With the code, the ECM also turns on the check engine light. That way the driver gets an instant notification to check the vehicle.

Possible Risks Associated with the P0456 Code

Although the P0456 doesn’t come with any performance issues, it can cause several problems.

• The car will fail the emission test
• If the leak grows bigger, it can cause a decrease in fuel economy
• The driver in some cases, may notice the fuel smell in the car. This is especially the case when parked in closed spaces.

See Also: P0442 Code: How To Fix Evaporative Emission Control System Leak

Dissecting the P0456 Code

Deciphering the P0456 Code – The Tech Perspective

An EVAP system is one of the most important systems that are lowering the overall dangerous emission of the vehicle. It works with other components, like the exhaust gas recirculation valve (EGR) and the catalytic converter to decrease the emission of those gases into the atmosphere.

The EVAP system is enclosed, and it should not release any fuel fumes out of the vehicle. When the engine is off, the fuel fumes are stored in the EVAP charcoal canister. When the engine is running, the gases from the canister are passed to the engine to be burned.

When the engine is running, the EVAP vent valve opens and closes to release the fumes. The fumes are moved to the engine to be used together with the air and fuel mix. That way, the engine saves some fuel, and the dangerous emissions are lowered.

The Core Components Involved with the P0456 Code

Several EVAP system components can be the cause of the P0456 EVAP fault code:

• The EVAP charcoal canister. The fuel fumes are stored in the charcoal pellets inside the EVAP canister. If the canister is damaged or leaking, that can cause a P0456 code
• The EVAP lines and hoses. If the lines and hoses are not connected properly or are damaged, they can let out some of the fuel fumes. That is also a common cause for the P0456 trouble code
• The EVAP purge valve. It is located on the engine, usually on the intake manifold. The EVAP purge valve is responsible for maintaining the levels of vapors that are going in and out of the EVAP canister. If the valve is stuck in a closed position, all the fuel fumes will go through the exhaust. That way, instead of burning the extra fumes in the engine, all the dangerous gases will end up in the air.

Also, some parts of the fuel system can be guilty of this error:

• A fuel tank. If the fuel tank filler neck or the tank itself is leaking, that can cause this error code
• A fuel cap. A damaged, loose, or missing fuel cap is a frequent cause for almost all EVAP system error codes.

Common Symptoms to Look Out for When Dealing with the P0456 Code

Like with all EVAP system-related issues, there are not many symptoms to look out for. The engine will work fine, and the driver will not notice any performance issues. That is one of the reasons why drivers often neglect these errors, which is a mistake.

But, there are a couple of symptoms that can point to a problem with a small EVAP leak.

• Turned on the check engine light. The ECM will automatically turn it on to notify the driver about the problem.
• Lowered fuel economy. Since the fuel fumes from the EVAP canister are not burned in the engine, it will require some additional fuel. That will lead to excessive fuel consumption.
• Failed emission test. When the time comes for the regular emission test, the vehicle will not pass it. If there are any problems with the EVAP leak error codes, they will be detected on the emission test
• Smell of fuel. The driver will notice a smell of fuel when parked in a closed space. Depending on the problem, the fuel smell can be felt even while driving.

Fixing the P0456 Code: A Comprehensive Walkthrough

Fixing a P0456 EVAP code demands proper diagnostics. Finding a small leak in the system is difficult, and it can demand some advanced tools and expert knowledge.

Step-by-Step Guide to Diagnosing and Fixing the P0456 Code

1. Connect the vehicle to a scan tool. Check for any additional error codes. If there are other codes, address them first
2. Inspect the fuel cap. Often a damaged fuel cap can cause not only small but also complex EVAP leaks. If you are not sure if the fuel cap is damaged, replace it either way. It is a cheap and simple fix, and it can resolve this issue
3. Check the EVAP canister for damage. If the canister cannot hold the fuel vapors, that will create a leak. If the canister is indeed damaged, replace it
4. Investigate the state of the EVAP lines and hoses. Most of the EVAP lines are going to the airbox. Inspect them for any cracks, damage, or leaks
5. Examine the EVAP purge valve. If the valve is not working properly that can lead to an increase in emissions and a leak fault
6. Look at the fuel tank. If it is dented or corroded, that can lead to leaking. If you detect a leak you should replace the faulty fuel tank.

Pro Tips for Efficiently Addressing the P0456 Code Issue

There are some advanced methods for testing and diagnosing the EVAP P0456 code.

You can visually inspect the purge valve for any damage to it or its wiring. But, an even better thing to do is to test it with a multimeter.

1. Remove the valve from the car
2. Set the multimeter to testing resistance (ohms)
3. Connect the probes of the multimeter to the power terminals of the valve. The readout values should be between 14 and 30 ohms, depending on the model. If not, the valve is faulty.

You can also test the purge valve with a hand vacuum pump.

1. The purge valve is closed when the engine is not working
2. Connect the vacuum pump to the purge valve and apply the vacuum
3. If the values change, that means that the valve is not working properly.

Sometimes it is hard to notice a leak on the EVAP lines. Then, you should test them with an EVAP smoke machine.

1. Close all the exit spots in the system, like the fuel cap and the purge solenoid
2. Connect the smoke machine to the car’s battery and turn it on
3. Find the entry point for the test and connect the machine to it. Usually, the place for this is the purge solenoid. Unplug the solenoid and then connect the adaptor to the machine to it
4. Close off the vent solenoid. For this, you will need an OBD-II automotive scanner. In the settings of the scan tool should be an option to close off the solenoid vent. If you do not have a scan tool, you can manually close it. It is located near the gas tank. The fuel tank pressure will rise once you close the solenoid
5. Look at the gauge on the smoke machine. If it rises to the top, there is a leak in the system
6. If there is a leak, grab a flashlight and look for it. The smoke machine will make it easy to identify the location of the leak.

See Also: P0442 Code: How To Fix Evaporative Emission Control System Leak

When to Call a Professional Mechanic for a P0456 Code Problem

There are several reasons for calling the mechanic regarding a P0456 problem:

• When you don’t have experience with DIY car mechanics, not every driver is a self-made mechanic. Some drivers leave all the fixing to the professionals.
• When you cannot diagnose the problem, finding a small leak is not easy. It is simpler to find a large leak. If you cannot find the leak, contact a professional
• If you do not have the proper tools. To be able to fully check the EVAP system you need some advanced tools. Those include the multimeter, the smoke machine, and the vacuum pump. If you do not have them and don’t want to spend money on them, visit the mechanic
• If you checked and fixed everything, and there is still an error. Sometimes a faulty ECM can wreak havoc in the system, resulting in wrong measurements and error codes. If you think that this is the problem, do not wait and go to the mechanic.

FAQs about the P0456 Code

Is It Still Safe to Drive with the P0456 Code?

Yes, it is safe to drive with a P0456 code. But do not wait too long to fix it. Avoid long trips, and fix the leak as soon as possible. You won’t be able to pass the emission tests, and the error may lead to an increase in fuel consumption.

How Much Does It Cost to Fix the P0456 Code?

Fixing a P0456 code depends on the underlying cause for it. These are the most common problems and how much does it cost to resolve them:

• A fuel cap: $20-$60
• A EVAP line: $50-$100
• The replacement charcoal canister purge valve: $150-$200
• The purge valve: $150-$200
• A fuel tank: $450-$3,000

Is an EVAP Leak the Same As A Gas Leak?

No, the EVAP leak is not the same as a gas leak. An EVAP leak is a leak of fuel vapors. A gas leak is a sign of a fuel leak somewhere in the fuel system.

How To Test a Purge Valve?

There are four ways to test the purge valve. We already covered one way to test it with the multimeter, called a resistance test and a vacuum test. Now, we will go through the other two methods, called a continuity test and a mechanical test.

1. To do a continuity test, you will need a multimeter.
2. Remove the purge valve from the car. Before removing it, wait at least 30 minutes with a turned-off engine. Separate it from the power terminal and unscrew the clamps holding to the hoses.
3. Set the multimeter to the continuity mode. This mode is commonly represented with a sound wave icon. To be sure, touch one probe of the multimeter with the other. That should trigger a beeping sound.
4. Place the multimeter probes into the purge’s valve power terminals. If you do not hear the beeping sound, then the valve is broken and needs to be replaced.

You do not need a multimeter for the mechanical test, also called the click test. When the engine is working it sends a signal to the valve to open and to allow the vapor to enter. When the valve opens, it makes a clicking sound. To check if there is a clicking sound on your vehicle’s valve, follow these steps:

1. Remove the purge valve from the car
2. Connect the valve to a 12V power source. For this, you can use the car’s battery and alligator clips.
3. Connect the valve’s power terminals to the battery. To do this, use the alligator clips. Connect one power terminal to the positive battery side and the other to the negative side.
4. Listen to the clicking sound. If this doesn’t result in any sound, that means that the valve is broken.

What Does “Small EVAP Leak Detected” Mean?

The system can detect small, medium, and large EVAP leaks. Some values put a certain leak into a category. If the measure values categorize the leak as a small one, the ECM will mark it as a small leak.

Need More Help with a P0456 Code?

Finding and fixing a small leak can be a difficult problem. It can demand a lot of tools and experience. If any obvious problems and fixes don’t work, you should contact the mechanic. An experienced mechanic has all the tools and knowledge needed to find and fix this problem.

Do not avoid fixing this issue. Yes, it doesn’t come with many symptoms, but your vehicle releases additional bad emissions, and it will not pass the emission tests. Also, you don’t want to end up driving in a car that smells of fuel. Also, isn’t it good to drive a car without any OBD-II codes, and without a check engine light?