Error code P0455 is another common code. It is usually set when the gas cap is loose or missing from the fuel tank. This triggers the vehicle’s computer as fuel fumes leaks from the tank into the atmosphere. Unburned droplets or raw fuel can contribute to smog and can affect breathing.

Error code P0455 means a large leak has been detected in the fuel vapor or lack of purge flow in the vehicle’s EVAP (Evaporative Emission System) control system.


Error code P0455 appears when the engine computer detects a large leak problem in the EVAP system. Normally, the EVAP system is sealed tight, as its main purpose is to keep gasoline vapor from escaping the fuel tank to the atmosphere. Fuel vapors are sent to the charcoal canisters through the hoses for storage. When the engine starts a purge control, a purge valve will open, allowing the vacuum to drain off the fuel vapors to the engine.

Common Symptoms

There will be no drivability problems, but there will be symptoms such as:

  • Check Engine light is on
  • Noticeable fuel odor from released fuel vapors

Possible Causes

The most common reason for this is the gas tank is left improperly sealed, though there could be other reasons as well, which may include:

  • Loose or improperly placed gas cap
  • Use of incorrect gas cap (not factory or original brand)
  • Leak or damage in EVAP system hose
  • Fuel tank or EVAP canister leak
  • Foreign object caught in the fuel filler cap
  • Defective fuel tank that doesn’t fully seal gasket
  • Damaged or split carbon canister

How to Check

If the EVAP system is properly sealed, the most common cause of leak can be in the gas cap, purge valve, vent valve, and connectors and hoses. With this error code, the first thing you need to check is the gas cap. If the gas cap is loose or open, then close it tight. This normally solves the ‘Check Engine’ light issue after a few miles of driving.

Many scan tools have enough information about this error code built-in from their online access, giving you the capability to diagnose the problem within minutes. All you need to do is get the code, and scan through their database for more details. Many also provide tips to solve the error code.

There will be times where it’s the gas cap itself that is problematic. Take a close look of the cap, inspect for damages on its rubber gasket and if necessary, replace your gas cap.

If you still can’t find obvious problems that lead to this error code, then it may be time to take your car to your dealer or mechanic. To pinpoint the exact leaking problem, mechanics would typically test the entire EVAP system using advanced scan tools and/or testing equipment called ‘smoke machine’ – it pushes smoke through the system to help detect the leak, as the smoke will escape through the leak.

Some mechanics also use vacuum tool. They block one piece of the system at a time such as the fuel tank, charcoal canister, and EVAP lines sections, pull its system from the vacuum and then check for leak rate. This approach however, needs a vacuum pump and time consuming.

How to Fix

The most common solutions to fix this error code are:

Check the Gas Cap

Simply remove the gas cap and replace it nice and tight to secure a sealed fuel tank. Clear the codes from your code reader tool, drive your car for a day and then check if the code comes back.

If gas cap doesn’t feel tight and secure, then it’s a good time to retire it and get a new one.

Check the EVAP System

Inspect the EVAP system for signs of damage such as cuts or holes along the tubes and hoses. You may notice a fuel smell or vacuum noise. Repair the problem as soon as possible.

Also, check the EVAP canister purge volume control solenoid valve. You can find this valve in your VQ35DE engine bay, mounted on the engine’s passenger side, near the intake manifold. You can find a set of vacuum hoses that run off the intake manifold to controller there.

Follow the vacuum line from your intake manifold to located the EVAP canister purge volume control solenoid.

Then, unplug the 2-pin weatherproof connector and test it for proper power and signal. You can do it by unplugging the connector and check the hoses for leaking. Fill a bottle with soapy water and gently spray it on the hoses to detect signs of leaks.

Then, move down the vacuum line until you see the EVAP resonator. It’s the plastic 1-way valve that leads to EVAP service port, usually covered by a green cap.

Take off the green cap by unscrewing, and then pressurize the EVAP system using the pressure tested to 0.2 – 0.4 psi. Take off the adaptor for EVAP service port and pressure tested and start looking for leaks.

Once you have found the leak, replace the vacuum line. This will usually fix the error code P0455.

For more information about different OBD II error codes, feel free to browse through our website. For professional mechanic assistance, Contact Us.