P0455 – EVAP system – large leak detected
P0455 reports a large leak in the evaporative-emissions system. Some diagnostic descriptions also refer to the absence of expected test flow.
Powertrain · Evaporative emissions (EVAP)
Open this code in the decoderMeaning and affected system
EVAP controls fuel vapour from the tank. This code describes a system-test result. It does not prove there is a visible hole in the tank or a leak in a line carrying liquid fuel.
Possible causes
- An incorrectly secured filler cap can contribute on vehicles with that design.
- An open connection or damaged vapour line can affect sealing.
- Valves and the vehicle’s particular testing arrangement also need consideration.
Possible symptoms
- A check engine light or filler-cap message may appear.
- Driving behaviour may be unchanged. Fuel smell cannot be inferred from the code alone.
Useful diagnostic considerations
- Record whether the warning followed refuelling or recent vehicle work.
- Check the fitted cap in accordance with the handbook; capless systems have their own instructions.
- Have recurring faults investigated with appropriate leak-testing equipment. Do not improvise a pressure test on the tank.
What this code does not prove
P0455 and P0442 concern the same system but report different test outcomes. Large and small are diagnostic categories, not reliable dimensions for a visible opening.
Related fault codes
Sources and interpretation
This explanation was editorially cross-checked against the technical sources below. Manufacturer documents concern particular vehicle applications; their thresholds and repair procedures must not be applied universally.
- Nissan: NTB13-097f — EVAP leak codes (2018)
- Ford: 2013 MY OBD System Operation Summary for Gasoline Engines
OBD-II code data: OBDex (CC0 1.0) · 196fddffb6ef
Editorial source review: .
The causes listed are possibilities without a likelihood ranking. This page cannot replace diagnosis of the vehicle. A code alone confirms neither a failed component nor that continuing to drive is safe. The actual condition, warnings, handbook and applicable manufacturer diagnostics determine the next step.