Evaporative Emission Control System Leak Detected (Large Leak)
What does P0455 mean?
The P0455 code means the vehicle's onboard diagnostic system has detected: Evaporative Emission Control System Leak Detected (Large Leak). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Strong fuel odor near the vehicle
- Possible emissions test failure
Probable Causes (Ranked by Likelihood)
- Missing or severely damaged gas cap Very High
- Disconnected or broken large EVAP hose High
- Failed or stuck-open vent valve High
- Cracked or split fuel filler neck Moderate
- Damaged charcoal canister Moderate
Step-by-Step Diagnostic Procedure
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Verify the gas cap is present and properly seated with an undamaged seal.
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Visually trace all large EVAP hoses (3/8 in or larger) from the fuel tank to the charcoal canister and to the engine.
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Command the vent valve closed with a scan tool and monitor fuel tank pressure -- pressure should hold if the system seals.
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Perform a smoke test with the vent blocked to locate the large leak. A large leak will be immediately visible.
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Inspect the filler neck where it attaches to the fuel tank for cracks or loose clamps.
Frequently Asked Questions
What is the difference between P0442 and P0455?
P0442 indicates a small leak (less than 0.040 in diameter) while P0455 indicates a large leak (greater than 0.080 in). A large leak is often as simple as a missing gas cap.
Is P0455 an emissions or safety issue?
Primarily emissions. The larger concern is the fuel odor, which represents raw hydrocarbon vapors. These are flammable and should be addressed promptly, especially near heat sources.