OBD codes / P0455
P0455
MinorEvaporative Emission System Leak Detected (Large Leak)
P0455 is the lowest-urgency category — no effect on performance or safety, only emissions. Tighten or replace the gas cap first; if the light clears after a few drive cycles, that was it. It will fail an emissions test until resolved, so fix it before inspection.
What this code means
The evaporative emission (EVAP) system seals fuel-tank vapors and routes them to be burned. P0455 means the computer detected a LARGE leak — the system couldn't hold pressure or vacuum at all. The number-one cause is a gas cap left loose, worn out, or missing, which is also the cheapest thing in OBD to fix. Beyond that, a cracked or disconnected EVAP hose, or a vent valve stuck open, are the usual culprits. Because it's a large leak, it's often easier to find than the small-leak codes. It has no effect on how the car runs.
Symptoms you might notice
- Check-engine light with no change in how the car drives
- Sometimes a noticeable fuel smell
- Frequently appears right after refueling
- Failed emissions test
What it costs to fix
Typical range: $20–$400 · about ~0.2–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Gas cap | $10–$35 | ~0–0.2 hrs |
| EVAP hose / line repair | $10–$80 | ~0.3–1 hrs |
| Vent valve | $30–$130 | ~0.3–1 hrs |
| Filler neck | $60–$250 | ~0.5–1.5 hrs |
Start with the gas cap — for a large leak it's the most common and cheapest cause. Hoses and the vent valve are still modest; a rusted filler neck is the priciest typical outcome.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0455 for my exact vehicle →
Frequently asked
Can I drive with P0455?
Yes — it doesn't affect how the car runs or its safety. The only real consequence is failing an emissions test, so drive normally and fix it at your convenience, ideally before inspection.
Will a new gas cap fix P0455?
Very often, yes — a large EVAP leak is most commonly a loose, worn, or missing gas cap. Tighten it until it clicks or replace a damaged one, then drive a few cycles; the light may clear by itself. If it returns, check the hoses and vent valve.
How much does it cost to fix P0455?
Frequently almost nothing — a gas cap is the cheapest OBD repair. Hoses or a vent valve are still modest. The priciest common cause is a corroded filler neck. A smoke test pinpoints a hidden leak.
What's the difference between P0455 and P0442?
P0455 is a LARGE EVAP leak (often a missing or loose gas cap, easier to find); P0442 is a SMALL leak (a tiny crack or seal that takes a smoke test to locate). Same system, different leak size.
Seeing P0455 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose P0455 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.