P0455 is reported as large evaporative-system leak. The next step depends on the full scan and the exact vehicle, not the code alone.
If braking, steering, power, temperature, smoke, or fuel smell is abnormal, stop safely; otherwise save the full scan and arrange diagnosis.
This Ford document supports only its stated code and vehicle context. The code alone cannot identify a failed part, prove that another make uses the same definition, or clear a car for driving. Compare your full scan with the current exact-vehicle service information.
Read the Ford original: Gasoline OBD System Operation Summary MY 2024–2025 Source date: 2024-04-16; research checked: 2026-11-01.
What this code means
P0455: Large evaporative-system leak. This is a source-scoped technical description. It does not prove that any named component has failed.
Namespace obd_reference
Make scope No exact vehicle application established
Definition status source supported definition vehicle applicability unverified
Why this exact code matters
The monitor reports a large EVAP leak. A loose cap is possible only if the vehicle has a compatible cap; do not transfer a cap check to a capless filler system.
Compare P0456: very small leak. A related code is a different observation, not a second diagnosis.
Evidence to save for this code
- Cap or capless filler type
- Fuel smell or visible leak
Keep the complete module scan and any accompanying warning; a single emissions code cannot show every relevant fault.
Ask for a measured diagnosis
- Is a controlled leak test needed to distinguish tank, hose, purge/vent and seal faults?
- Does a circuit fault require electrical diagnosis instead of leak-part replacement?
The EVAP: fuel-cap check is conditional, not the whole diagnosis guide has the shared system checks and after-repair questions. Those broad checks apply to a system, while the meaning above is specific to P0455.
Vehicle and scanner limits
We have not verified this code for every make, model, year or engine. A generic emissions scanner may not read the body, chassis, transmission or EV module that holds related faults. Compare the full scan with the owner manual and manufacturer service information.
Sources and scope
- Ford — Gasoline OBD System Operation Summary MY 2024–2025 Document: 2024-04-16 · Research checked: 2026-11-01
- Ford — OBD System Operation Summary, gasoline 2020–2023 update Document: 2023-10-23 · Research checked: 2026-11-01
- Ford — 1999 Powertrain Control/Emissions Diagnosis DTC descriptions Document: date not recorded · Research checked: 2026-11-01
- Ford — 10-1-3 Document: 2010-01-08 · Research checked: 2026-11-01
- Chrysler / NHTSA — PE13-016 Chrysler Enclosure 9A Document: 2013-08-09 · Research checked: 2026-11-01
Research snapshot: 2026-11-01. Source documents may have newer revisions. Verify current instructions and VIN eligibility with the manufacturer.