P0455 is an OBD-II code indicating a large vapor leak in your vehicle's EVAP (evaporative emission control) system. The most common cause is a missing or improperly sealed gas cap — a $5–$15 fix. Unlike small-leak code [P0456], large leaks are often found by visual inspection alone, and most P0455 repairs cost under $100 in parts.
P0455 vs. P0456: Large Leak vs. Small Leak
| P0455 (Large Leak) | P0456 (Small Leak) | |
| Leak size threshold | 0.040 inches or larger | 0.020 inches |
| Most common cause | Missing gas cap, disconnected hose, stuck-open vent valve | Worn gas cap seal, cracked hose, leaking purge valve |
| Ease of diagnosis | Easier; often found by visual inspection or listening for hissing | Harder; usually requires a smoke machine |
| Typical repair cost | $5–$200 | $5–$250 |
| Related codes | [P0442], [P0441] | [P0442], [P0441] |
What Does Code P0455 Mean?
P0455 means the PCM detected a large vapor leak in the EVAP system — the sealed network of hoses, valves, and a charcoal canister that prevents fuel vapors from escaping the gas tank into the atmosphere.
Symptoms of P0455
- Check engine light (MIL) on — steady, not flashing; P0455 alone will not cause a flashing light
- Noticeable fuel smell near the fuel tank, gas cap, or charcoal canister area (typically under the rear of the vehicle), especially in warm weather; more pronounced than with P0456
- Hissing sound near the gas cap or under the vehicle — a disconnected hose or stuck-open vent valve may produce an audible hiss when the fuel tank is pressurized
- No change in engine performance
What Causes a P0455 Code?
- Missing or improperly sealed gas cap ($5–$15) — most common cause.
- Disconnected or cracked EVAP hose ($5–$20) — a fully disconnected line creates a larger pressure drop than a cracked hose and is more likely to trigger P0455 than P0456.
- Stuck-open vent valve ($20–$60) — must close during the EVAP leak test to seal the system; often appears alongside [P0446]
- Cracked charcoal canister ($50–$150) — road debris impact or fuel overfilling creates a large enough opening to trigger P0455
- Damaged fuel tank or fuel filler neck ($50–$500) — corrosion from road salt or a puncture from road debris; more common on northern-climate vehicles
- Failed fuel tank pressure (FTP) sensor ($30–$80)
How to Diagnose P0455
- Check the gas cap. Verify it is present, seated, and tightened until it clicks. Inspect the rubber O-ring for cracks, missing chunks, or debris. Replace if damaged, clear the code, and drive two to three drive cycles.
- Read all stored codes. [P0441] (incorrect purge flow) points to the purge valve. [P0446] (vent control circuit) points to the vent valve.
- Visually inspect all EVAP hoses. Trace every vapor line from the fuel tank to the canister and from the canister to the engine intake. Look for disconnected, cracked, melted, or rodent-chewed hoses — a large leak from a disconnected hose is often visible without tools.
- Perform a smoke test. If visual inspection does not reveal the leak, pump low-pressure smoke into the EVAP system through the purge valve port. Smoke escaping from any hose, valve, or canister reveals the leak location.
How to Fix P0455
- Replace the gas cap — match to your vehicle's year, make, and model; tighten until it clicks
- Reconnect or replace the EVAP hose
- Replace the vent valve
- Replace the charcoal canister
How Much Does It Cost to Fix P0455?
| Repair | DIY Part Cost | Shop Cost (Parts + Labor) | Repair Time |
| Gas cap replacement | $5–$15 | $5–$15 (no labor) | 1 min |
| EVAP hose reconnection/replacement | $5–$20 | $75–$200 | 30 min–1 hr |
| Vent valve replacement | $20–$60 | $100–$250 | 30 min–1 hr |
| Fuel tank pressure sensor replacement | $30–$80 | $150–$350 | 1–2 hrs |
| Charcoal canister replacement | $50–$150 | $200–$400 | 1–2 hrs |
| Fuel filler neck replacement | $50–$150 | $200–$500 | 1–3 hrs |
| Smoke test (diagnosis only) | $0 (borrow/rent) | $60–$150 | 30 min |
Check the gas cap and EVAP hoses before paying for a smoke test or parts.
Can You Drive With a P0455 Code?
Yes. A large EVAP leak does not affect engine operation, vehicle safety, or drivetrain function. The lit check engine light also masks any new codes that may appear for unrelated and potentially serious problems. Fix P0455 as soon as practical.
P0455 by Make
Chevy / GM Chevy Silverado (2007–2018, 4.8L/5.3L/6.2L V8), Chevy Equinox (2010–2017), and Chevy Cruze (2011–2016) are among the highest-volume P0455 vehicles.
On the Silverado, the EVAP vent valve solenoid is the most frequent cause after the gas cap. GM mounts the vent valve on the frame rail under the rear of the truck, where road debris, mud, and water accelerate solenoid failure.
Toyota Toyota Tacoma (2005–2015) and Tundra (2007–2014) trigger P0455 at higher rates than Toyota sedans. The charcoal canister and vent valve are mounted in exposed underframe positions where off-road use and road debris can crack the canister or damage the valve.
Ford Ford F-150 (2011–2020) and Escape (2013–2019) commonly set P0455. On the F-150, the gas cap and vent valve are the most frequent causes.
Hyundai Hyundai Elantra (2011–2016) and Tucson (2010–2015) trigger P0455.