P0455 Evaporative Emission Control System Leak Detected (gross or large leak)

The code P0455 is set when the engine computer recognizes a large leak in the Evaporative emission control system (EVAP). The vehicle's EVAP system is sealed, it's main purpose is to prevent gasoline vapors in the fuel tank from escaping into the atmosphere. The most common culprit is the gas cap that is left open or not closed properly, although there could be other problems, read more below.

What can cause the code P0455:

- gas cap left open or not closed properly
- faulty gas cap or damaged gas cap seal
- faulty or stuck-open vent control valve (could also be called vent valve or EVAP vent solenoid)
- damaged or cracked charcoal canister
- cracked or disconnected EVAP hose
- stuck open purge valve (solenoid)

Examples:

- In some Nissan and Infiniti vehicles including Altima, Rogue, Versa, Pathfinder and QX4, 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. It can be tested by applying battery voltage to the vent control valve terminals. When voltage is applied, the vent control valve should produce and audible click. If there is no click, the vent control valve must be replaced. For some models, the vent control valve design has been modified. An updated part can be ordered from a Nissan dealer. This thread at TitanTalk.com shows how it looks.
Nissan also has published a technical service bulletin (TSB) for the 2005-2007 Pathfinder recommending to install a filter kit if the code P0455 is caused by a faulty vent control valve.
- In some late 90's to early 2000's Dodge, Jeep and Chrysler vehicles, cracks in the rubber hoses and elbows that connect some of the components of the EVAP system are fairly common to cause the code P0455 and other EVAP codes. The rubber hoses are typically used to connect the rigid plastic lines to the service port, canister and other parts. Some rubber hoses are located under the hood, others are under the car and close to the charcoal canister. The cracks could be small and difficult to find. The diagnostic process requires careful inspection. Thanks to the authors of this thread at WranglerForum and this thread at DodgeForum for posting the pictures.
- 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.
- According to the Mazda TSB, in some 2004-2006 Mazda 3 and Mazda 6 vehicles, the code P0455 could be also caused by a stuck-open purge valve. The purge valve can be tested with a vacuum pump, see the photos here.
- In many Volkswagen and Audi vehicles, the faulty purge valve (N80 in VW literature) commonly to causes the P0455 and some other codes.

What needs to be checked:

Loose gas cap
Loose gas cap

The EVAP system is sealed and the most common components that can cause a leak are the gas cap, vent valve and purge valve and the hoses and connectors, see the diagram below. The first thing to check with this code is the gas cap. If it was left open or loose, close it tight and the "Check Engine" light should reset itself after a few drive cycles. Sometimes a 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. If no obvious problem is found, the next step is to take your car to a mechanic or your dealer. Typically to find a leak, a mechanic would need to test the whole EVAP system using an advanced scan tool and the testing equipment known as a 'smoke machine'. The "smoke machine" pushes the "smoke" through the system, so that any leak can be visually detected.

How the EVAP system vent control works

Evaporative System (EVAP) diagram

EVAP system simplified diagram

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 is 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.

Q: I left the gas cap open in my car and the check engine light came on. I just closed the gas cap properly, but the light is still on. Any thoughts?

A: It may take a couple drive cycles for the light to reset itself after the gas cap was closed properly. This is because the vehicle's emission system runs the self tests when the car is driven. Usually 40 minutes to 1 hour of normal driving should be enough for the system to check itself.

Q: I have Nissan Rogue and my Check Engine light is on. I had it scanned at the auto parts store and the code is P0455. What could it be?

A: The code P0455 means an EVAP system leak detected. As always, check the gas cap first. A common problem in this vehicle is a bad vent control valve. It's installed at the charcoal canister at the back of the car, close to the right rear wheel. Your mechanic can easily check it. It's a solenoid valve that closes when the voltage is applied. If the vent control valve is bad, make sure to use the new updated part from Nissan, it's not very expensive and is easy to install.

Q: The check engine light came on in my 2003 Dodge Durango. I had it scanned at AutoZone, the code is P0455. I already checked my gas cap and it's tight. The truck drives fine. What could it be?

A: One particular area that often causes an EVAP leak in these trucks is a cracked rubber hose near the EVAP service port. It's located on the driver side in the engine compartment; the service port is that "T" connection with the little green cap. If the problem is not there, take your truck to a repair shop to have the EVAP system tested with the smoke machine. It may cost from $40 to $110, but it works pretty well for detecting EVAP leaks.