P0455: Evaporative Emission System Leak Detected (Large Leak)
Key takeaways
- P0455 means the computer could not hold pressure or vacuum in the fuel vapor system, which points to a large opening such as a missing or loose gas cap.
- It is safe to drive; the engine runs normally and the only real costs are fuel vapor, a failed emissions test and a light that hides other problems.
- Check the gas cap first, then have a shop smoke-test the system if the code returns.
- Most fixes cost $15-$350; a new charcoal canister is the expensive end at $300-$800.
What P0455 means
Your car found a big opening in the system that traps gasoline vapor from the tank. The scanner name is “Evaporative Emission System Leak Detected (Large Leak)”. The EVAP system stores tank vapor in a charcoal canister and later lets the engine burn it. To check for leaks, the computer seals the system with the vent valve and pulls a vacuum or applies a small pressure, then watches whether it holds. If the pressure change never happens, or disappears fast, it sets P0455. Emissions rules require the computer to find openings as small as 0.020 inch, so “large” here is anything from a loose cap to a disconnected hose. The code often shows up a day or two after a fill-up, because that is when the cap was last touched.
Is it safe to drive?
Yes. P0455 does not change how the engine runs. The practical costs are a little fuel lost as vapor, a likely emissions test failure, and a lit check engine light that can hide a new, more serious code.
The answer changes if you smell raw gasoline strongly around the car or see fuel dripping. That is a liquid leak, not an EVAP fault, and it needs attention the same day.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Gas cap loose, missing or worn seal | Cap does not click, cracked or flattened O-ring | $0 to tighten, $15–$40 new |
| Cracked or disconnected EVAP hose | Smoke test shows smoke at the hose | $100–$300 |
| Purge valve stuck closed or vent valve stuck | Scan tool command test, vacuum check at the valve | $120–$350 |
| Filler neck rusted or its seal leaking | Smoke at the filler area, rust at the neck | $250–$600 |
| Charcoal canister cracked or clogged | Smoke at the canister, dust or fuel in the vent line | $300–$800 |
What to check first
- Check the gas cap. Tighten it until it clicks, and look at the rubber seal. If it is cracked, a new cap costs less than a diagnosis. Our loose gas cap guide covers this step by step.
- Clear it and drive. EVAP is one of the few families where this is a fair test. Give it a week of normal driving with the tank neither full nor near empty.
- Look under the car at the hoses near the tank and canister for anything hanging loose.
- Smoke test. If the code returns, a shop pumps visible smoke into the system to find the opening. This usually costs $100–$200 and is faster than guessing at parts.
- Check bulletins. Nissan and Infiniti publish EVAP leak guidance for their 2012-and-newer models. GM has bulletins for 2019–2023 Silverado and Sierra trucks where dust gets into the canister and sets P0455 with related EVAP codes.
What it costs
The cheap outcome is a tightened or new cap, $0–$40. The common outcome is a hose, purge valve or vent valve at $100–$350 plus a smoke test. The expensive outcome is a canister or filler neck, up to about $800. A smoke test before buying parts is the difference between one repair and three. If you are not sure which part the smoke pointed to, ask our AI mechanic.
Related codes
P0455 often appears with P0442 (small leak) or P0456 (very small leak) once the problem gets worse or better. P0457 is the code many cars use specifically for a loose or missing cap. Purge and vent circuit codes like P0441 and P0446 point to the valves. If you smell fuel too, read car smells like gas.
What owners report to NHTSA
72 complaints filed with NHTSA mention P0455, 47 of them since 2015, across 54 different models. The component owners most often filed it under: fuel/propulsion system.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| GMC ENVOY | 4 | 2003, 2004 |
| FORD FUSION | 4 | 2010, 2011 |
| CHEVROLET TRAILBLAZER | 3 | 2004 |
| JEEP GRAND CHEROKEE | 3 | 1997, 2002, 2004 |
| FORD ESCAPE | 3 | 2005, 2010, 2011 |
| KIA SOUL | 3 | 2015, 2018 |
Manufacturer service bulletins that name P0455
192 technical service bulletins and manufacturer communications filed with NHTSA mention P0455, from 23 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- INFINITI INFINITI, bulletin 10183904: 2012 AND NEWER INFINITI VEHICLES; EVAP LEAK DTC P0442, P0455, P0456 INFORMATION This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- NISSAN NISSAN, bulletin 10184003: 2012 AND NEWER NISSAN VEHICLES; EVAP LEAK DTC P0442, P0455, P0456 INFORMATION This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- NISSAN TITAN (2012, 2013, 2014, 2015), bulletin 10208948: EVAP LEAK DTC P0442, P0455, P0456 INFORMATION This bulletin has been amended. See AMENDMENT HISTORY on the last page. Please discard previous versions of this bulletin.
- GMC SIERRA 2500 (2020, 2021, 2022, 2023), bulletin 11010573: This technical bulletin provides repair information to correct a customer concern of Evaporative DTCs P0442, P0446, P0455 or P0449, Caused by Dust Intrusion into the Evaporative Canister.
- CHEVROLET SILVERADO 3500 (2020, 2021, 2022, 2023), bulletin 11010573: This technical bulletin provides repair information to correct a customer concern of Evaporative DTCs P0442, P0446, P0455 or P0449, Caused by Dust Intrusion into the Evaporative Canister.
- GMC SIERRA 3500 (2020, 2021, 2022, 2023), bulletin 10239087: This technical bulletin provides repair information to correct a customer concern of Evaporative DTCs P0442, P0446, P0455 or P0449, Caused by Dust Intrusion into the Evaporative Canister.
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
How long after tightening the gas cap does P0455 go away?
The computer only reruns the leak test under certain conditions, often after the car sits overnight with the tank between roughly a quarter and three-quarters full. It usually takes a few days of normal driving. A scan tool can clear it right away, but the test still has to pass later.
What is the difference between P0455 and P0442?
Size. P0455 is a large leak, like an open cap or a disconnected hose. P0442 is a small leak, down to a pinhole or a cracked seal. The checks are similar, but a large leak is usually easier to find.
Can a bad purge valve cause P0455?
Yes. On many cars the leak test uses engine vacuum pulled through the purge valve. If that valve is stuck closed, the system never builds vacuum and the computer reads it as a large leak. A purge valve stuck open often causes rough starts after refueling.
Is P0455 dangerous?
Usually not. It becomes a concern if you smell raw fuel around the car or see wetness under the tank, because that is liquid fuel, not just vapor. Get that checked the same day.
References
- NHTSA Office of Defects Investigation — complaint flat files (snapshot 2026-09-23)
- NHTSA — manufacturer communications / technical service bulletin flat files
- 13 CCR 1968.2 — California OBD II requirements, evaporative system monitoring (e)(4), Cornell LII
- EPA, Do You Drive a 1996 or Newer Car or Light Truck? OBD consumer brochure, EPA420-F-02-016 (2021 archive)