P0455: Evaporative Emission System Leak Detected (large leak)
The computer found a large leak in the EVAP system, often a missing or loose gas cap.
What P0455 means
P0455 appears when the EVAP system cannot build or hold enough vacuum during its self test. RepairPal explains this is typically caused by an air leak, and lists a missing or loose fuel cap, a damaged filler neck, damaged EVAP hoses, a damaged fuel tank and other leaks as the most common reasons. A large leak is usually something obvious, such as a cap left off, a hose that came loose, or a vent or purge valve stuck wide open. The engine computer runs this test only under certain conditions, often after a cold soak with the tank between about a quarter and three quarters full, so after a fix the code may take a few days of driving to confirm. KBB notes the code will not change how the car performs, but strong fuel smells should be checked. If the cap is fine, shops run a smoke test, which usually finds a large leak quickly. Fixes are often cheap.
Common symptoms
- Check engine light on
- Fuel smell near the car
- Usually no change in driveability
- Failed emissions test
- Possible trouble filling the tank
Most common causes
- Missing or loose gas cap
- Damaged gas cap seal or filler neck
- Disconnected or cracked EVAP hose
- Purge valve stuck open
- Vent valve stuck open
- Damaged charcoal canister or fuel tank
What to check yourself first
Check the gas cap first; RepairPal lists a missing or loose cap as one of the most common reasons for P0455. Tighten it until it clicks, clear the code and drive for a few days. Look under the car near the tank for a hose that has popped off.
Typical fixes and what they cost
| Fix | Typical cost | Note |
|---|---|---|
| Replace gas cap (shop price) | $138-$150 | If the cap is missing, damaged or will not click. |
| EVAP smoke test to find the leak | $61-$90 | A smoke test is the standard way to find EVAP leaks. |
| Replace EVAP purge valve | $210-$251 | If the purge valve is stuck open. |
| Replace EVAP canister (includes vent valve on many cars) | $558-$643 | For a cracked canister or failed vent valve. |
Typical US price ranges for parts and labor, not quotes. Your shop should confirm the cause with a diagnostic before replacing parts.
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Related codes
- P0442 Evaporative Emission System Leak Detected (small leak)
- P0456 Evaporative Emission System Leak Detected (very small leak)
- P0457 Evaporative Emission System Leak Detected (fuel cap loose/off)
- P0440 Evaporative Emission System
- P0446 Evaporative Emission System Vent Control Circuit