P0455

EVAP System Leak Detected - Large Leak

Evaporative emissions (EVAP) Generic OBD-II Low

What it means

P0455 means the evaporative emissions system has a large leak — fuel vapor that should be sealed in and burned by the engine is escaping to the air. It does not affect how the car runs or starts. The most common cause is a loose or worn gas cap, so start there before chasing hoses or valves.

Low

Can I keep driving? Yes — the car drives normally; this is an emissions leak, not a running problem, so fix it at your convenience (start with the gas cap).

Real-world scan data

Seen in

1,216

scans in the past year

Found in

0.2%

of scans

0.3%

of scans that found faults

Appears alongside · share of P0455 scans

P0441in 17.4% of scans

P0420in 15.3% of scans

P0442in 14.6% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Occasional smell of fuel vapor near the car
Fails an emissions / smog test
Slightly reduced fuel economy from lost vapor

Common causes

Most likely first

Loose, missing, or worn gas cap — by far the most commonLikely
Cracked or split EVAP hose, or a disconnected lineCommon
Stuck-open or leaking vent or purge valveCommon
Cracked charcoal (EVAP) canisterLess often
Damaged fuel filler neck or a leaking fuel-tank sealLess often

How to diagnose & fix

Work through it in order

Remove and reseat the gas cap until it clicks, then clear the code and drive a few cycles — this fixes many P0455s.
If it returns, inspect the cap seal for cracks or wear and replace a worn cap.
Visually inspect EVAP hoses and connections from the tank forward for splits or disconnections.
Have the system smoke-tested to pinpoint the leak — the fastest way to find a large one.
Test the vent and purge valves and inspect the charcoal canister; replace whatever failed.

FAQ

Quick answers

Is it safe to drive with P0455?+

Yes. It only means fuel vapor is escaping instead of being captured; the engine runs and drives normally. Repair it to pass emissions and stop the vapor loss.

Can I just clear P0455?+

You can, but it returns until the leak is fixed. Try tightening or replacing the gas cap first — if that was the cause, it will stay gone.