What it means
A large leak has been detected during the EVAP system pressure or vacuum test — large enough that the system cannot hold pressure for the diagnostic interval. Typically a missing fuel cap, disconnected hose, or split canister.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The evaporative emissions system seals the fuel tank and vapor lines so fuel vapors can be stored and routed to the engine. P0455 sets when the module detects a large leak or cannot establish the expected seal during its EVAP test.
Common causes
Most likely first.
- Fuel cap missing or not seated
- EVAP hose disconnected
- Charcoal canister cracked
Symptoms
- Check engine light on
- Possible smell of fuel near tank or engine bay
- Failed emissions inspection
- Loose-cap warning may appear
How to diagnose it
- Read freeze-frame data and check for a loose-cap warning and other EVAP codes.
- Check that the fuel cap is present, undamaged, and seated correctly.
- Inspect accessible EVAP hoses and connections for a disconnected line, split, or obvious damage.
- Check the charcoal canister and its connections for cracks or damage.
- If the source is not visible, perform a manufacturer-approved EVAP smoke or leak test.
Common fixes
- Refit the fuel cap securely or replace it if damaged.
- Reconnect a detached EVAP hose.
- Replace a split or damaged EVAP hose.
- Replace a cracked charcoal canister if testing confirms the leak.
Can I keep driving?
The vehicle is generally drivable if it runs normally, but escaping fuel vapor can cause a fuel smell and the vehicle may fail an emissions inspection. If the fuel smell is strong or there is visible liquid fuel, stop safely and arrange prompt inspection.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.