P0455: Evaporative Emission System Leak Detected (Large Leak)
Updated Last reviewed September 15, 2026By CarFaultIQ Editorial Team
Verify with official recall databases, service records, a mechanic inspection, and local market data before relying on this summary.
At a glance
Quick diagnostic answer
The EVAP system seals fuel vapors and periodically pressure- or vacuum-tests itself. When it can't hold pressure at all, the computer flags a large leak.
SeverityLowUrgencyUrgency not yet verifiedEvidenceSource notes available
OBD code
P0455
System/category
Evaporative System
Severity
Low
Structured severity term
Urgency
Urgency not yet verified
Can I drive?
Usually OK to drive short-term
No mechanical risk — this is an emissions vapor leak. Fix it to pass inspection and stop fuel vapor loss.
Repair/cost band
$ · Minor
Estimate band only — actual cost varies by region, parts availability and labor rates.
Vehicle applicability
Universal across makes and years.
Current applicability note is free text
Computed rule output may be more cautious than stored content and is never used to soften safety-critical risks.
Short answer
P0455 means the fuel vapor system has a large leak — and the most common cause is simply a loose, damaged or missing gas cap. Check the cap before paying anyone.
SeverityLowDrive?Usually OK to drive short-termRepairDIY – Easy
Key takeaways
Check the cap before paying anyone.
Most common causes: loose, damaged or missing fuel cap and cracked evap hoses or filler neck.
First diagnostic step: remove and reseat the gas cap; inspect its seal.
Can I still drive with this?
Usually OK to drive short-term
No mechanical risk — this is an emissions vapor leak. Fix it to pass inspection and stop fuel vapor loss.
SeverityLow
Low
Diagnostic flow
What it meansThe EVAP system seals fuel vapors and periodically pressure- or vacuum-tests itself.…
Check this firstRemove and reseat the gas cap; inspect its seal
Likely causeLoose, damaged or missing fuel cap
Can you drive?Usually OK to drive short-term
P0455 is a generic OBD-II code, which means it carries the same core definition on every make — what differs is which causes are most likely on your engine.
Work the diagnostic steps below in order. They are sequenced from cheapest-and-most-common to most expensive, which is exactly the order a fair shop should follow.
Structured DTC reference
What P0455 means
A large leak in the fuel vapour system
A trouble code identifies the circuit or monitored condition that failed its test. It does not, by itself, identify the failed part or prove the same cause on every vehicle.
Cause categories to discriminate
Split fuel vapour hose
Loose or worn fuel cap
These are structured diagnostic hypotheses, not a parts-replacement list. Vehicle context, symptoms, operating conditions, and test results determine which remain supported.
Severity and drivability
The code alone is not enough to assign one universal severity or “safe to drive” answer. Stop driving for loss of braking or steering, severe overheating, oil-pressure loss, a fuel leak or fire risk, or any rapidly worsening safety symptom.
The EVAP system seals fuel vapors and periodically pressure- or vacuum-tests itself. When it can't hold pressure at all, the computer flags a large leak.
Common symptoms
Check engine light with no drivability change
Occasional fuel smell near the car
Failed emissions test
Likely causes
Loose, damaged or missing fuel cap
Cracked EVAP hoses or filler neck
Stuck-open vent or purge valve
Damaged charcoal canister
Diagnosis steps
Remove and reseat the gas cap; inspect its seal
Clear the code and drive a normal cycle — many cases end here
If it returns, smoke-test the EVAP system to find the leak
Test vent and purge valve operation
Inspect the filler neck for rust or damage
What a mechanic should check
A smoke test finds EVAP leaks in minutes — it should be the second step after the cap, not a last resort.
Vehicle applicability
Universal across makes and years.
Repair actions / cost band
$ · Minor
Estimate band only — actual cost varies by region, parts availability and labor rates.
P0455 — vehicles with official records naming this code
P0455 is named in NHTSA-published manufacturer communications or investigations for 139 vehicle families, including:
Nissan Versamodel years 2007-2009, 2012-2022 · 29 records
A code named in a manufacturer communication means the document refers to it for those vehicles. It is not a diagnosis of any car, and it does not mean the code is common on that vehicle.
Frequently asked questions
Is it really just the gas cap?
Very often, yes. Reseat it, clear the code or wait a few drive cycles, and see if it returns.
Can I drive with P0455?
Yes — there's no mechanical risk. You're venting fuel vapor and will fail emissions testing until it's fixed.
What if the cap didn't fix it?
A smoke test is the efficient next step; guessing at valves and hoses wastes money.
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