Ford Mustang P0456: EVAP System – Small Leak

The most frequent trouble code with the Ford Mustang Is the Code P0456. This is the trouble code that you get when you plug your Mustang in to an OBDII scanner. The code P0456 indicates that the evaporative emissions control system has a tiny leak. This code is often found with or related to P0420,P0441 and, very rarely, P0440.

Normally, P0456 does not pose a threat to the Mustang's driveability. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible.

While the trouble code may state that there is a “small leak” in the EVAP system of your Ford Mustang, it is actually referring to the amount of pressure lost, and not the physical size of the leak. This can happen in very small amounts.

Ford Mustang P0456 Definition

P0456 stands for a universal OBDII Trouble Code. It means that no matter what make or model vehicle you have, this code will still mean the exact same thing. Technically speaking, it stands for:

Systems Leakage in the Smallest Detail – Evaporative Emission System

The EVAP captures any fuel vapor in the fuel tank. They are then sent to the engines intake for ignition. When there is a small leak in the Ford Mustang’s EVAP system, it will throw the P0456 OBDII Code. If there is a large leak, it’ll throw P0455.

Ford Mustang P0456 OBDII Code Symptoms

The P0456 code is usually not accompanied with any other symptoms than those listed. The smell of gas The service engine soon light.

Particular attention should be paid to the smell of fuel near the fuel tank or fuel filler tube.

The EVAP process deals with fuel vapors directly. If these vapors are leaking from the system, you’ll often smell them faintly while operating the vehicle. But, it won’t affect the way the engine itself runs. The EVAP system is for fuel vapor and does not affect the performance of your Mustang's engine.

Mustang P0456 Trouble Code Reasons

P0456 can be triggered by many factors in your Ford Mustang. If your Mustang has warned you at all in the last few months that the fuel cap was off when it wasn’t, then replacing it would be a great first step.

Below are the top most probable problems that could throw the code. These were listed alphabetically, in some order.

• Evap Hose– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. This can lead to the code P0456. You should look for a hole or a tear in the code. This is the leading cause of code.
• Vapor Canister Purge Valve– One of the most common causes of the P0456 code is the vapor canister purge valve. It’s really easy to replace. You'll need to identify and remove a few clips.
• Fuel Tank Sending Unit– It is possible for the gasket that attaches the fuel sending unit to the gas tank to go bad. It can lower the tank pressure, which could throw out the code.
• Fuel Cap– A bad fuel cap can cause the code to be thrown for sure. Often, you’ll get a message informing you that the fuel cap is off even when it is on. It may be worth your time to get that message and a P0456 to ensure you don't waste any money.
• Fuel Filler Neck– There is often a gasket where the fuel filler neck connects with the gas tank. It is possible for this gasket to dry, particularly if vehicles spend a lot of time in dry environments. When it dries out, the fuel tank can’t hold pressure anymore.

Ford Mustang Diagnostics - P0456

To diagnose the problem with your Ford Mustang's P0456, a mechanic can use a variety of tools. These are some of the common diagnostics that can be done for the code.

• The mechanic will check to make sure there are no other codes. It is easier to diagnose problems if there are more codes. That’s because when they appear together in certain combinations, there will often only be only a few conditions that will throw any combination of codes at one time.
• Once the mechanic has determined the trouble codes associated with P0456, he or she will usually Take a look at the EVAP system. These include the line and purge valve.
• A mechanic will examine the gas cap and verify that it is able to withstand high pressure. If you are getting a warning that your gas cap is off, even when it’s on, replacing it will more than likely clear this code.
• Monitor and check the pressure in your fuel tank.
• The mechanic will then perform the following tests after completing the above-mentioned checks:
• A smoke test, and they’ll use a scan tool to confirm that the EVAP solenoids and valves are operating properly.

Here’s a pretty good video on diagnosing these leaks from Scotty Kilmer, if you are interested:

Most common P0456 fixes

These are some of the most popular Mustang P0456 repairs:

• Replacing the gas cap
• Replacing EVAP lines
• Replace charcoal canister
• Change the fuel tank

You should start with the gas caps and move on to the fuel tanks. This is because the gas caps are the easiest to replace and the least costly.

Here’s a great video on How to test your gas tank.

We wish you all the best in finding out why your Ford Mustang is throwing the P0456 error code. This should help. Please feel free to add anything below.

Are P0456 Serious Concerns?

While P0456 is not going to cause the Mustang’s engine to stop running, it should not be treated lightly. Fuel leaks could be a problem. Check your tank regularly to make sure there is no fuel leaking. You should immediately take it in for repair or replacement.

Please leave comments below if you have any suggestions. Thanks!