Diagnostic code
P0455 Code: Large EVAP System Leak Detected
P0455 means the fuel vapor system cannot hold pressure or vacuum during its self-test, and the leak appears large. A loose gas cap is a common simple cause, but hoses, valves, and the charcoal canister can also leak.
Can I drive?
Usually yes if the vehicle runs normally, but repair it before emissions testing and investigate quickly if fuel odor is strong.
Repair range
$25-$700
Scanner note
Basic OBD-II scanner with live data
Plain-English Meaning
P0455 means the fuel vapor system cannot hold pressure or vacuum during its self-test, and the leak appears large. A loose gas cap is a common simple cause, but hoses, valves, and the charcoal canister can also leak.
Common Causes
Symptoms
- Check engine light
- Fuel smell near vehicle
- Failed emissions test
- No obvious drivability change
Diagnostic Steps
- 1Inspect and tighten the gas cap
- 2Check the gas cap seal for cracks
- 3Inspect visible EVAP hoses
- 4Smoke-test the EVAP system
- 5Command purge and vent valves with a scan tool if available
Confusable And Related Codes
P0442
Compare →P0442 means the evaporative emissions system detected a small vapor leak. The vehicle may drive normally, but the fuel vapor system is not sealing tightly enough during the onboard leak test.
P0440
Compare →P0440 is a broad EVAP system fault. Instead of identifying a specific leak size or valve circuit, the computer is saying the fuel vapor control system did not pass its expected self-test.
P0446
Compare →P0446 means the EVAP vent control system is not behaving as expected. The vent valve may be stuck, blocked, electrically faulty, or unable to seal the fuel vapor system during testing.
P1450
Compare →P1450 usually means the vehicle cannot relieve fuel tank vacuum as expected during EVAP operation. It is often associated with purge or vent control problems, a restricted vapor path, or a fuel tank pressure reading that does not change nor
FAQ
Will tightening the gas cap fix P0455?
It can if the cap was loose or leaking, but the light may need several drive cycles to turn off.
Is P0455 dangerous?
It is usually low severity, but a strong fuel smell should be inspected quickly.
Does P0455 affect fuel economy?
Usually not much, though it can cause vapor odor and emissions failure.
This page is educational and is not a substitute for hands-on vehicle diagnosis. Source notes: Code meaning verified against OBD-II reference sources; explanation is original.