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Figuring out why your Check Engine Light is on means deciphering OBD-II (or “OBD2”) codes, and that can be kind of annoying. That’s why Car Bibles did it for you! You’re welcome, now let’s get into solving your issue.

OBD2 Code P0455: What It Means

This code reads as “Evaporative Emissions (EVAP) Large Leak Detected” meaning there’s a large leak in the system the car uses to control vapors evaporating from the fuel tank. Generally, this code is fairly straightforward.

Likely Symptoms 

Here’s what you may experience due to the P0455 code:

  • The Check Engine Light might be on. That’s probably what brought you to this page in the first place, right?
  • Poor fuel economy.
  • A fuel smell. This depends on the size and location of the leak, but it is rare.

Probable Causes

Here’s what could be causing the issue:

  • The gas cap is open or isn’t sealing anymore. The gas cap is part of sealing the EVAP system and trapping those fuel vapors, and needs to secure the gas tank.
  • The charcoal canister is cracked. While rare, some cars have their charcoal canisters in vulnerable locations, like an early-2000s Subaru WRX. They can be struck by road debris and cause a huge leak.
  • EVAP lines, fuel filler neck are torn. The rubber lines around the fuel tank can get old and perish over time, causing a leak. This is usually only applicable to older vehicles.

What Part Is Potentially Affected?

This code often gets tripped when the car’s gas cap wasn’t tightened down enough after filling up, so your first step might just be to make sure that’s cranked down tight. If it is, you’ll also want to think about how old that gas cap is. If your car’s getting close to a decade on the road, the seal on that cap might have hairline cracks you can’t even see. At worse, it’s some small rubber lines that perished and need replacement, usually doable at your own home.

Possible Fixes

Here are the most common fixes to remedy the P0455 code:

  • Make sure your gas cap is tight. Just turn it a few more clicks (if possible) and see if the check engine light vacates the premises.
  • Replace the gas cap. If tightening it doesn’t work, get a new gas cap from your local auto parts store. They’re usually pretty cheap. 
  • Smoke test the EVAP system. Budget smoke testers are everywhere now. It will tell you more about what lines are perished, or where the leak is coming from, by simply pumping (non-flammable) light smoke into the gas tank.
  • Replace EVAP lines going from gas tank to charcoal canister. Usually, this is the last thing to replace in a short diagnostic tree. On older cars, the lines crack and allow fuel vapor to escape. Auto part stores stock the line needed in bulk.
  • Replace the charcoal canister. A last ditch, freak accident sort of thing would result in the charcoal canister to crack and leak. A quick visual will tell you what you need to know.

Finding The Parts You Need

Now that you’ve figured out what’s wrong with your hooptie, let’s talk about where you’re gonna find that part’s replacement.

There are plenty of places you can buy auto parts from, but Car Bibles gets paid if you click this Advance Auto link so that’s the one we’re serving up. Advance Auto Parts also has delivery, curbside pickup, and a host of helpful diagrams to aid your repair!

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