P0455 — EVAP System Leak Detected (Large Leak / Gross Leak)
Can drive — fix at your convenience.
What P0455 means
P0455 indicates the EVAP system detected a large (gross) leak, meaning a significant amount of fuel vapor is escaping. The biggest and easiest cause to rule out is a gas cap that's missing, loose, or has a bad seal, but it can also be a disconnected or cracked hose or a stuck-open valve. It doesn't usually affect performance, but the leak is larger than the small-leak codes.
Common symptoms
- Check engine light is on
- Noticeable gasoline odor
- Failed emissions test
- Gas cap missing, loose, or clicking abnormally
- No real change in how the car drives
Common causes
- Missing, loose, or unsealed gas cap
- Disconnected or badly cracked EVAP hose
- Purge or vent valve stuck open
- Damaged or cracked charcoal canister
- Leak at the filler neck or fuel tank seal
Typical repair cost
$20 – $350
Varies by vehicle and root cause.
Frequently asked questions
Is it just the gas cap?
Surprisingly often, yes. A missing or loose gas cap is one of the most common triggers for a large-leak code. Make sure the cap is on and tightened until it clicks first, then a replacement cap ($20-60) before any larger repair.
Can I drive with a P0455 code?
Yes, in most cases. The car runs normally and it's safe for normal driving. You might smell fuel, though, so check the cap immediately and get the system inspected soon.
How much does it cost to fix?
If it's the gas cap, just $20-60. A cracked hose, stuck valve, or canister repair generally costs $100-350 with diagnosis and labor.
Is a P0455 large leak serious?
It's still considered low severity for drivability, though the leak is bigger than the small-leak codes. It won't hurt the engine, but it releases more fuel vapor and will fail emissions, so fix it promptly.