Subaru Forester P0456: EVAP System – Small Leak

The most frequent trouble code with the Subaru Forester Is the Code P0456. This is the trouble code that you get when your Forester gets plugged in to a OBDII scanner. A P0456 code indicates that there may be a slight leakage in the evaporative exhaust control system. This code is often found with or related to P0420,P0441 and, very rarely, P0440.

The P0456 issue is not usually a threat to your Forester'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 Subaru Forester, it is actually referring to the amount of pressure lost, and not the physical size of the leak. They can also be very minor.

Subaru Forester P0456 Definition

The universal OBDII code P0456 can be used to diagnose trouble codes. It means that no matter what make or model vehicle you have, this code will always mean the same thing. Technically the code is:

System Leakage of Small Size – Evaporative Emission System

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

Subaru Forester 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.

The fuel filler tube or around the fuel tank should smell particularly strong.

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 technology deals only with the fuel vapor but not how the Forester engine runs.

Forster P0456 Trouble code Causes

P0456 can be triggered by many factors in Subaru Foresters. If your Forester 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 System 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. It should be checked for tears or holes. 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 will need to locate and take out 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. This could cause a drop in tank pressure which can throw off 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.

Subaru Forester Diagnostics - Page 0456

To diagnose the problem with your Subaru Forester'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 usually check for any additional trouble codes. A mechanic will usually check for additional trouble codes to help diagnose the problem. 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.
• The mechanic will normally determine what trouble codes are associated with P0456. Check out the EVAP System. It includes the purge valve and line as well as the canister.
• 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.
• Monitoring and checking the fuel tank pressure is a must.
• 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:

The Most Popular P0456 Fixes

Below are the top Forester P0456 solutions:

• Replacing the gas cap
• Replacing EVAP lines
• Replace charcoal canister
• Replacing 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 check your gas cap.

You will need to solve the problem quickly. We trust this helped. You can add any additional information by leaving a comment.

Are P0456 Serious Concerns?

While P0456 is not going to cause the Forester’s engine to stop running, it should not be treated lightly. There could be fuel contamination. Check your tank regularly to make sure there is no fuel leaking. It is best to have it checked and/or dealt with immediately.

Feel free to add anything to the article by leaving a comment. Thanks!