Subaru Forester P0457: EVAP System – Leak Detected

P0457 This is an example of a common problem code for the Subaru Forester. The code refers to a number you receive when your Forester is plugged into a OBDII scanner. It indicates that an Evaporative Emission Control System (EVAPS) leak is P0457. Similar to P0455 for large leaks and P0456 for small leaks, it is also called P0457.


Subaru Forester P0457 Diagnosis


The P0457 issue is not usually a threat to your Forester's driveability. Certainly anytime the service engine soon light is on though, it’s good to deal with it as soon as possible.


Índice de Contenido
  1. Subaru Forester P0457 Definition
  2. Subaru Forester P0457 OBDII Code Symptoms
  3. Treeper P0457 Trouble Code Reasons
  4. Subaru Forester Diagnostics - P0457
  5. The Most Popular P0457 Fixes
  6. Do you consider P0457 to be a serious concern?

Subaru Forester P0457 Definition

P0457 can be used as an OBDII universal trouble code. The code can be used regardless of the make and model of the vehicle. Technically, the code stands for:

System Leak – 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 leak in the Subaru Forester’s EVAP system, it will throw the P0457 OBDII Code.


Subaru Forester P0457 OBDII Code Symptoms

P0457 Subaru Forester

The P0457 code is usually not accompanied with any other symptoms than those listed. The smell of gas And the service engine soon light.

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

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 operation of your Forester's engine.


Treeper P0457 Trouble Code Reasons

P0457 is a trouble code that your Subaru Forester can trigger. 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.

These are some of the most frequent problems that can throw off the code. They're listed in alphabetical order, from the most likely to the least.


  • 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 code P0457. You should look for a hole or a tear in the code. This is the main problem that can cause the code.
  • Vapor Canister Purge Valve– One of the most common causes of the P0457 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. You may not get the message but a P0457. This will save you time and 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 - P0457

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Subaru Forester P0457. The most commonly used methods to diagnose this code are:

  • Most mechanics 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 P0457, he or she will usually Take a look at the EVAP system. It includes the line, purge valve and canister.
  • To ensure that the cap can withstand pressure, the mechanic will check it. 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:



Below are the top Forester P0457 solutions:

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

It is best to begin with the gas cap, and then work your way up to the fuel tanks. The gas cap is the most difficult and cost-effective item to replace.

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 P0457. This information is hoped to be helpful. You can add any additional information by leaving a comment.


Do you consider P0457 to be a serious concern?

While P0457 is not going to cause the Forester’s engine to stop running, it should not be treated lightly. There could be fuel contamination. You should pay extra attention to the level of your fuel tank and ensure that you're not leaking fuel. It is best to have it checked and/or dealt with immediately.

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


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