Many years I am working in the automotive industry and I have seen this code P0455 often. There are many reasons to cause the P0455 code. But first you have understood what is code P0455 for and its definition.
Generally, P0455 code is the evaporative system detected a large leak. These are potential fail component in the evaporative system:
- Fuel Cap
- Leak At Gas Cap
- Evaporative Emission (EVAP) Purge Solenoid Operation
- Intermittent Leak Detection Pump (LDP) Monitor Failure
- Natural Vacuum Leak Detection (NVLD) Valve
- Evaporation Emission System Leak
- Leak Detection Pump (LDP) Component Leak
How Do I Fix Code P0455?
Most common leaks are loose or leaking gas cap or split evaporative system (EVAP) hoses. Even a small split is enough to set the code. Best way to confirm if your vehicle has EVAP leak, is to perform a smoke test. Another test is to force the evaporative system in test monitor by using advanced scan tool.
If smoke test is perform and the leak cannot be found, you may lose the cap and tightened it again. If you see the smoke at the gas cap, then replace the gas cap. The most common hoses to split are hoses on both sides of the service port.
In some place you cannot see the smoke, you need to use a mirror to inspect all hoses. You can feel all the hoses with your fingers, sometime you can feel a split. If possible, you be able to see the o-ring for fuel pump is bad, sometime you can see this by removing rear seats
How Do You Fix A Large EVAP Leak?
If your vehicle has a large Evaporative System leak detected, most likely the gas cap is bad.
The best way to find the EVAP leak is to smoke test the whole system. Using advanced scan tool to access functional test to seal system. Apply vacuum to a vacuum operated vent block and see if vacuum decays. If vacuum decays, the vent block may be defective. The problem is most likely an actual leak and not functional failure. When the leak is repaired, clear the code and use EVAP monitor test to force EVAP monitor to run and set codes quickly if problems persist.