One of the most common trouble codes with the Subaru Liberty is the P0456 code. This trouble code references a number that is given to you when you plug your Liberty into a OBDII scanner. P0456 Indicates that there is a small leak in the evaporative emission control system. It often appears with, or is related other codes, such as P0420, P0441, and very often P0440.
P0456 is normally not an immediate threat to the drive-ability of your Liberty. 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 Liberty, it is actually referring to the amount of pressure lost, and not the physical size of the leak. These leaks can be really small.
Subaru Liberty P0456 Definition
P0456 is a universal OBDII trouble code. This means that regardless of which make or model of vehicle, the code will mean the same thing (Liberty or not). The code technically stands for:
System Small Leak – Evaporative Emission System
The EVAP system captures all fuel vapor from the fuel tank and sends them to the engines intake in order to be ignited in the normal combustion process. When there is a small leak in the Subaru Liberty’s EVAP system, it will throw the P0456 OBDII Code. If there is a large leak, it’ll throw P0455.
Subaru Liberty P0456 OBDII Code Symptoms
P0456 code will typically not be accompanied by any noticeable symptoms other than the smell of gas and the service engine soon light.
You should particularly notice the smell of fuel around the fuel tank area or fuel filler tube.
The EVAP system deals directly with fuel vapors. 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 deals with fuel vapor, and not the running of the engine in your Liberty.
Liberty P0456 Trouble Code Causes
There are many things that can cause the P0456 trouble code to trigger in your Subaru Liberty. If your Liberty 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.
Here are the most common problems that will throw the code, presented in order (somewhat) from most to least likely:
- Evap System Hose– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. This will cause the P0456 code. Look for either a tear or hole in it. This is one of the most common issues that causes the 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. There are a few clips that you need to find and remove.
- Fuel Tank Sending Unit– It is possible for the gasket that attaches the fuel sending unit to the gas tank to go bad. This can reduce tank pressure and throw 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. If you are getting that message, plus a P0456, it may save you a ton of time and money to replace the fuel cap and see if it goes away.
- Fuel Filler Neck– There is often a gasket where the fuel filler neck connects with the gas tank. This gasket can dry out, especially with vehicles that spend their time in dry climates. When it dries out, the fuel tank can’t hold pressure anymore.
P0456 Diagnosis- Subaru Liberty
A mechanic has a wide range of instruments at his disposal to diagnose what would be causing the P0456 in your Subaru Liberty. Here are the most common things that are done to diagnose the code:
- The mechanic will typically check to see if there are any other trouble codes. The more trouble codes there are, the easier it can be to diagnose a 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.
- After ascertaining what trouble codes appear with the P0456, the mechanic will typically inspect the EVAP system. This includes the purge valve, line, and canister.
- The mechanic will inspect the gas cap to make sure that it can handle 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.
- The fuel tank pressure will be checked and monitored.
- After for the checks and fixes listed above, the mechanic will perform two 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:
Most Common P0456 Fixes
Here are the most common Liberty P0456 fixes:
- Gas cap replacement
- EVAP line replacement
- Replace charcoal canister
- Replace the fuel tank
Of all the items listed above, it would be wise to start with the gas cap and work your way to the fuel tank, since the gas cap is far and away the easiest and least expensive items to replace on here.
Here’s a great video on how to test your gas cap.
Good luck figuring out what is causing your Subaru Liberty to throw the P0456 code. We hope this helps. If there is anything that you feel like you could add, please feel free to leave a comment below.
Is P0456 a Serious Concern?
While P0456 is not going to cause the Liberty’s engine to stop running, it should not be treated lightly. You could have a fuel leak. Pay extra attention to your tank level and make sure you are not leaking fuel. We recommend taking it in and/or dealing with it right away.
If you feel like there is anything that you could add to this article, please leave a comment below. Thanks!