P0455 Trouble Code definition
System Gross Leak Evaporative Emission
The Code P00455 code is often associated with P0440 code.
What the P0455 code means
P0440 is the general code for a problem with the Fuel Evaporative Emission System. The P0455 code specifically indicates a large leak in the system, not a fuel leak, but one in the vapor recovery system.
What causes the P0455 code?
The leak can be caused from a variety of components. The most common is related to the fuel filler cap which could be missing, not correctly installed, not sealing properly or may be damaged to the top of the filler neck.
The next most frequent problem is a leak in a hose. Hoses on the breather system tend to crack with age including the large connecting hose on the filler neck to the tank. The Evaporative Emission System has a purge valve to regulate pressure in the system and this will need to be checked by a technician.
Vehicles with a charcoal filter on their evaporative system need to check the filter for cracks, damage, or leaks. The fuel tank itself may be leaking or the gasket where the fuel level sensor, pressure sensor, and fuel pick attach to the tank may be leaking. See the manufacturer's diagram of the system to verify components and their locations. Note that even if the code indicates a large leak, it may actually be fairly small.
What are the symptoms of the P0455 code?
P0455 will generally be preceded by the Check Engine Light coming on the dashboard’s display. There can be a noticeable gasoline fuel smell in the filler area or tank area. It is also possible the smell could also becoming from the evaporative lines to the engine intake system.
How does a mechanic diagnose the P0455 code?
P0455 is diagnosed with an OBD-II scanner. The technician should then reset the OBD-II fault codes and road test the vehicle to see if the code comes back and he can observe this by watching it live on his scanner while driving.
If the code comes back, then the mechanic will need to do a visual inspection to determine any obvious leaks. If no leaks are seen, then the next step is to use a smoke test on the system to look for a leak. If there is no leak noted, then there may be a sensor issue that will need to be tested by the manufacturer's instructions as each system is slightly different.
Common mistakes when diagnosing the P0455 code.
Diagnostic errors are largely due to not following the procedure. The process is a logical and economically sound way to proceed. If you need a fuel cap, they are usually less than $30, but other components such as the Evaporative Emission System purge valve can cost several hundred dollars
How serious is the P0455 code?
P0455 code will not affect the way the car drives, but if the fuel odors are very strong or have obvious fuel leaks, take the car to a qualified technician as soon as possible. The system leak failure can cause excessive fuel consumption in certain circumstances so it is best to take to a technician at your first opportunity. Occasionally, if no problems are found, the technician can reset the fault codes, then retest. Note, that to do proper testing the fuel tank, it should be 1/4 to 3/4 full to ensure proper conditions to test. Often times, if the Check Engine Light came on immediately at start up, the OBD-II system can be reset and the vehicle will operate normally.
Often times, if the Check Engine Light came on immediately at start up, the OBD-II system can be reset and the vehicle will operate normally.
What repairs can fix the P0455 code?
Potential repairs to P0455 are:
Replacing the gas cap if it doesn't tighten or seal
Replacing the fuel filler neck if it's damaged or has anything that would prevent it from sealing with the cap
Repairing any hose problems
Additional comments for consideration regarding the P0455 code.
Many vehicles with mileage over 100,000 have momentary sensor problems that usually occur during start up or prolonged stress situations on the drive train. If the Check Engine Light comes on and the vehicle seems to be operating normally, the OBD-II system can be reset using the scanner and the problem may not reoccur. This is why it is important to verify the fault and reset it before doing any repairs.
Need help with a P0455 code?
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This article originally appeared on YourMechanic.com as P0455 OBD-II Trouble Code: System Gross Leak Evaporative Emission and was authored by John Nelson.