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).
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.
Related codes
Often seen with P0455
Read & clear P0455 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX