P0455 Evaporative Emission Control System Leak Detected (Large leak)

The P0455 code signals a large leak in the Evaporative Emission Control System (EVAP). This sealed system prevents fuel vapors accumulating in the fuel tank from escaping into the atmosphere. One common culprit is an improperly closed or open gas cap, but other issues could be at play.

Causes:

• Gas cap left open or not closed properly.
• Faulty gas cap or damaged gas cap seal.
• Faulty fuel capless unit.
• Faulty or stuck-open EVAP Vent control valve (a.k.a. canister vent valve.).
• Stuck open EVAP Purge valve (solenoid).
• Faulty EVAP Leak detection unit.
• Leak in the fuel neck.
• Cracked, damaged or disconnected EVAP hose or line.
• Cracked or damaged charcoal canister.

Symptoms:

In most cases, the Check Engine light will come on, but the car with the code P0455 will not show any driveability issues. The loose fuel filler cap warning light or message may also be displayed. In some cases, you may detect the smell of fuel vapors around the vehicle. This is more likely if there is a significant leak in the evaporative emission control system.

In some GM trucks and other vehicles with this code, the fuel tank may also be hard to fill. We also know that often the code P0455 comes together with the code P0456: Evaporative Emissions System - Small Leak Detected. It's a very similar code caused by the same problems, only the code P0456 points to a small leak in the EVAP system.

What Needs to be Checked:

The first thing to check with this code is the gas cap. If it is left open or loose, close it tight and the "Check Engine" light should reset itself after a few drive cycles.

Sometimes the gas cap itself can go bad. Have a closer look at it, if there is visible damage to the cap or its rubber gasket, it must be replaced.

Testing the EVAP system for leaks without proper equipment is difficult. For this reason, If no obvious problem is found, the next step is to take your car to your mechanic or a local dealer for diagnostics. They will have to test the EVAP system for leaks. They can do that using a scan tool and a testing equipment known as a 'smoke machine'. The "smoke machine" (in the photo) pushes the "smoke" through the system, so that leaks can be visually detected.

Another way is to search for a common issues that can cause the code P0455 in the Make Year and Model of your vehicle. Often, you will find that someone already found the fix and posted it on some of the forums or on YouTube.

Also, try searching for service bulletins mentioning the Year, Make and Model and the code P0455. Car makers issue service bulletins for some common problems with their vehicles. Service bulletins also contain information about the possible warranty coverage.

Examples of Common Problems

The Acura service bulletin 21-007 for the 2021 Acura TLX says that the fuel main flap unit may have stuck open, causing a DTC to set. The bulletin recommends replacing Replace the Fuel Capless Unit. We know that some Honda vehicles of this generation also often have the same code caused by a faulty fuel capless unit.

The GM service bulletin 09-06-04-028D says that the code P0455 as well as some other codes in a number of 2007-2010 GM trucks could be caused by water intrusion into the vent valve. The bulletin advises to replace the vent control valve and modify the original installation.

A faulty purge valve is common to cause the code P0455 in some Hyundai vehicles. In Hyundai technical literature it's called Purge Control Solenoid Valve or PCSV.

In many Volkswagen and Audi vehicles, the faulty purge valve (N80 in VW literature) also commonly causes the P0455 and some other codes. Read more: Purge valve: how it works, symptoms, problems, testing.

According to the service bulletin 040 dated April 2018 for the 2012-2017 Kia Rio, a stuck open EVAP vent valve that in Kia technical literature is referred to as Canister Close Valve (CCV) can cause codes P0455 and P0456. The solution is to replace the CCV with an improved part.

The service bulletin 25-002-15 REV. B for the 2015 Jeep Grand Cherokee and Dodge Durango says to replace the purge valve hose if it shows any splits and codes P0455 or P0456 are present.

How the EVAP System Works

The Evaporative System (EVAP) traps the fuel vapors from the gas tank and temporarily stores them in the charcoal canister.

When the engine is running and other conditions allow, the fuel vapors are purged from the charcoal canister into the engine to be burned.

The Evaporative System is sealed and there are a number of sensors that allow the engine computer to detect a leak. The diagnostic trouble code P0455 - Evaporative Emission System Leak Detected (Large Leak) means that the engine computer has detected a large EVAP system leak.

Vent Control Valve:

In some Nissan and Infiniti vehicles as well as some GM trucks, as well as many other cars, the code P0455 is often caused by a bad vent control valve. The vent control valve is located at the back of the vehicle, at or near the charcoal canister.

The vent control valve can be tested by applying battery voltage to the vent control valve terminals. When voltage is applied, the vent control valve should produce an audible click and close. Normally the vent control valve is open. If there is no click, or the valve is not working properly, it must be replaced.

We know that for some vehicles, the design of a new OEM vent control valve has been modified. An updated part can be ordered from a dealer. Read more: EVAP Vent valve (solenoid): how it works, problems, testing.