P0455
Evaporative Emission System Leak Detected (Large Leak)
Quick answer: P0455 means evaporative Emission System Leak Detected (Large Leak). Fixing the underlying cause typically runs $0 to $520 at an independent shop. Usually safe to drive.
- Severity
- Low
- Safe to drive?
- Usually safe to drive
- Typical repair
- $0 to $520
- Most likely cause
- A loose, missing, cracked, or aftermarket gas cap that does not seal (check this before you pay anyone)
What P0455 means
Your fuel system is sealed to keep gasoline vapor from escaping into the air. The computer periodically pressurizes or vacuums that system to test the seal, and P0455 means it found a large leak. In practice, the number one cause is embarrassingly simple: a gas cap that was not tightened, or whose rubber seal has hardened with age.
Common symptoms
What drivers usually notice with this code.
- Check-engine light with no change at all in how the car drives
- A faint gasoline smell around the vehicle, especially after filling up
- The light often appears within a day or two of a fill-up
- Failed emissions test
- No other symptoms whatsoever in most cases
Common causes
Ranked from most to least likely.
- 1A loose, missing, cracked, or aftermarket gas cap that does not seal (check this before you pay anyone)
- 2A cracked or disconnected evap hose, which are plastic and get brittle with age
- 3A purge valve stuck open, holding the system open when it should be sealed
- 4A failed vent valve, often mounted near the rear of the car where road salt gets it
- 5A damaged filler neck, sometimes from rust around the fuel door
- 6A cracked charcoal canister, more common on vehicles that have been off-roaded or rear-ended
Can I keep driving?
Yes, this code affects fuel vapor emissions, not how the car runs, so it is safe to drive while you sort it out.
Severity: Low. A flashing check-engine light always means stop, whatever the code says.
Ballpark cost
What P0455 usually costs to fix
A range, not a quote. What you pay depends on your vehicle, your area, and which of the causes above turns out to be the real one.
Typical parts and labor at an independent shop. Dealer rates run higher.
That spread is wide on purpose. P0455 points at a system, not a single part, so the real answer depends on what the diagnosis finds. Use the range to know what to expect. If an estimate comes in higher, it usually means the specific repair is more involved, and it is always fair to ask what is included.
Next steps
What to do next
Before anything else, remove your gas cap, wipe the sealing surface and the filler neck, and reinstall it until it clicks at least three times. Drive for a few days: a large number of P0455 codes clear on their own once the seal is restored. If the light comes back, ask for a smoke test rather than a parts swap, since a $20 gas cap and a $455 vent valve produce the same code and only a smoke test tells them apart.
Walk in informed
Ask for the diagnosis in writing and which test confirmed it, so you understand exactly what is being fixed. Fixxr shows you what the job typically costs near you, so you can approve the work with confidence.
Sources & further reading
- NHTSA — Check for vehicle safety recalls — look up open recalls for your vehicle by VIN, free
- FTC — Auto repair basics — your consumer rights at the repair shop
- AAA — Car repair and maintenance costs — independent guidance on what repairs should cost
Cost ranges and guidance reviewed July 2026.
P0455 FAQ
P0455 questions, answered
Can I drive with a P0455 code?
Yes, this code affects fuel vapor emissions, not how the car runs, so it is safe to drive while you sort it out.What does the P0455 code mean?
Your fuel system is sealed to keep gasoline vapor from escaping into the air. The computer periodically pressurizes or vacuums that system to test the seal, and P0455 means it found a large leak. In practice, the number one cause is embarrassingly simple: a gas cap that was not tightened, or whose rubber seal has hardened with age.What are the most common causes of a P0455 code?
The most likely causes, roughly in order, are a loose, missing, cracked, or aftermarket gas cap that does not seal (check this before you pay anyone); a cracked or disconnected evap hose, which are plastic and get brittle with age; a purge valve stuck open, holding the system open when it should be sealed; a failed vent valve, often mounted near the rear of the car where road salt gets it. Before anything else, remove your gas cap, wipe the sealing surface and the filler neck, and reinstall it until it clicks at least three times. Drive for a few days: a large number of P0455 codes clear on their own once the seal is restored. If the light comes back, ask for a smoke test rather than a parts swap, since a $20 gas cap and a $455 vent valve produce the same code and only a smoke test tells them apart.How much does it cost to fix a P0455 code?
Fixing the underlying problem behind a P0455 code typically runs $0 to $520 at an independent shop, including parts and labor. The exact figure depends on your vehicle and which part turns out to be at fault.
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