P0455
Low severityEvaporative Emission System Leak Detected (Large Leak)
Safe to drive. P0455 is almost always a loose, missing or cracked gas cap. Tighten or replace it before spending money on anything else.
What does the P0455 code mean?
The P0455 code means your car detected a large leak in the Evaporative Emission (EVAP) system — the system that captures fuel vapors from your gas tank so they don’t escape into the air.
About 9 times out of 10, the cause is the simplest possible: a gas cap that isn’t sealing properly. It can be loose, missing, cracked or just old and worn out. Less often, the leak is in an EVAP hose or a valve.
Can you keep driving with a P0455 code?
Yes, it’s safe to drive. P0455 doesn’t affect how the engine runs — you’ll lose a tiny bit of fuel as vapor and your car will fail an emissions inspection while the light is on, but nothing will break. Tighten the gas cap, drive a few cycles, and see if the light clears.
What causes a P0455 code?
- Loose, missing or cracked gas cap~60%
- Damaged EVAP hose~20%
- Faulty purge valve or vent valve~15%
- Charcoal canister problem~5%
How to diagnose a P0455 (check these first)
- Tighten the gas cap firmly until it clicks several times.
- Inspect the gas cap’s rubber seal — cracked or hardened = replace it ($10-$25).
- Look for cracked or disconnected EVAP hoses near the tank and engine.
- If the code returns after a new cap, a shop smoke-test finds the leak in minutes.
P0455 repair cost
Typical US ranges including parts and labor (varies by vehicle):
| New gas cap | $5 – $25 |
| EVAP hose replacement | $50 – $150 |
| Purge or vent valve | $80 – $200 |
Tools & parts that help
A $20 OBD-II scanner lets you clear the code yourself after tightening or replacing the gas cap, so you don’t have to drive 50 miles waiting for it to reset on its own.
See gas caps & OBD-II scanners ›P0455 — Frequently asked questions
Is it safe to drive with a P0455 code?
Yes. P0455 doesn’t affect how the engine runs – it just means fuel vapors are escaping. Tighten the gas cap and drive normally.
Can a gas cap really cause a P0455?
Yes – it’s by far the most common cause. Loose, missing, cracked or worn-out gas caps account for most P0455 codes.
How long after tightening the gas cap will the code clear?
Usually after 2 to 5 complete drive cycles (starting cold, driving, parking, repeating). A scanner can clear it instantly.
Will P0455 fail an inspection?
Yes. An active check engine light with P0455 will fail an emissions or smog inspection until it’s resolved.
Related codes
General guidance based on the standard definition of the P0455 code. A real diagnosis depends on your make, model, mileage and other symptoms. When in doubt, have a professional confirm the cause before replacing expensive parts.