Subaru Forester P0455 Code Diagnosis

This is one of the most commonly encountered trouble codes for the Subaru Forester Is the Code P0455. The trouble code refers to a number you receive when your Forester is plugged into an OBDII scanner. The trouble code P0455 indicates that there are a Large leak It is part of the evaporative emission controller system. This code is often found with or related to P0420,P0441 and, very frequently, P0440.

Your Forester's driveability is generally not affected by P0455. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though. It's often associated with P0442. For more information, see Subaru Forester OBDII code P0442

Subaru Forester P0455 Definition

P0455 refers to a general OBDII trouble code. 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 Gross Leak – Evaporative Emission System

The EVAP captures any fuel vapor in the tank. They are then sent to the intake of the engine to start the combustion process. When there is a large leak in the Subaru Forester’s EVAP system, it will throw the P0455 OBDII Code.

Subaru Forester P0455 OBDII Code Symptoms

A P0455 Code will usually not cause any symptoms except the ones listed below. The smell of gas And the service engine soon light. The slightest drop in fuel economy may also be noticeable.

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

The EVAP system is responsible for fuel vapors. If these vapors are leaking from the system, you’ll often smell them faintly while operating the vehicle.

Treeper P0455 Trouble Code Reasons

Many things can trigger the P0455 code in Subaru Forester. The most frequent problems that trigger this code are:

• Hose for Evap System– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. This can lead to the P0455 code. 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 P0455 code is the vapor canister purge valve. It’s really easy to replace. It is important to identify and remove a few clips.
• The Faulty Charcoal Caister– The charcoal canister is often the cause of P0455.
• 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 P0455 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. The gasket may dry out especially if the vehicle is in dry conditions. When it dries out, the fuel tank can’t hold pressure anymore.

Subaru Forester Diagnostics - Page 0455

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Subaru Forester P0455. The most commonly used methods to diagnose this code are:

• A mechanic will usually check for additional 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 P0455, he or she will usually Check out 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.
• Following the inspections and repairs, the mechanic will conduct two more tests.
• 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:

While the trouble code may state that there is a “large leak” in the EVAP system of your Subaru Forester, the actual leak will most likely still look rather small. The “large” really is referring to how much pressure is being lost.

The Most Popular P0455 Fixes

These are some of the more common Forester P0455 fix:

• 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 check your gas cap.

We wish you all the best in finding out why your Subaru Forester is throwing the code P0455. We trust this helped. You can add any additional information by leaving a comment.

Do you consider P0455 to be a serious concern?

While P0455 is not going to cause the Forester’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.