Practical checks and shop questions for Leak/purge/vent codes; save evidence before replacing parts.
This is a non-invasive owner checklist, not an OEM repair procedure or permission to drive.
This reference supports the stated topic only. Model, model year, equipment, current rule or individual vehicle conditions may differ; check the original source before acting.
Read the Ford original: Gasoline OBD System Operation Summary MY 2024–2025 Source date: 2024-04-16; research checked: 2026-11-01.
Codes in this diagnostic topic
These codes share a system-level checklist, but their distinct numbers and meanings are shown below. A code here does not prove a particular vehicle has every listed fault. Use the exact code row and full scan.
| Code | Meaning | Vehicle scope |
|---|---|---|
| P0440 | Evaporative-emission system fault | Exact vehicle scope unverified |
| P0441 | Purge-flow performance mismatch | Exact vehicle scope unverified |
| P0442 | Small evaporative-system leak | Exact vehicle scope unverified |
| P0443 | Purge-control electrical circuit fault | Exact vehicle scope unverified |
| P0446 | Vent-control electrical circuit fault | Exact vehicle scope unverified |
| P0452 | EVAP pressure/switch signal low | Exact vehicle scope unverified |
| P0453 | EVAP pressure/switch signal high | Exact vehicle scope unverified |
| P0455 | Large evaporative-system leak | Exact vehicle scope unverified |
| P0456 | Very small evaporative-system leak | Exact vehicle scope unverified |
| P0457 | Evaporative leak with cap-loose/off context | Exact vehicle scope unverified |
| P0496 | Excessive/unexpected purge-flow context | Exact vehicle scope unverified |
| P0498 | EVAP vent-control signal low | Exact vehicle scope unverified |
| P0499 | EVAP vent-control signal high | Exact vehicle scope unverified |
| P1450 | Fuel-tank vacuum cannot be relieved as expected | Ford |
| P2404 | EVAP leak-pump sensing performance mismatch | Exact vehicle scope unverified |
| P2418 | Evaporative switching-valve control circuit | Exact vehicle scope unverified |
Save the evidence first
- Cap or capless filler type
- Fuel smell or visible leak
- Recent refueling, fill level and exact code
- Other purge/vent circuit codes
Safe owner checks
- If there is fuel odor/leak or smoke, stop inspection and obtain help.
- For a cap-equipped vehicle, visually check seating and obvious seal damage as the owner manual allows.
- Do not force open a capless mechanism.
Questions for a qualified technician
- 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?
- Does Ford 10-1-3 apply after physical faults are checked?
Common wrong turns
- Not all EVAP codes are gas-cap faults.
- Do not use homemade smoke generators, shop air or ignition sources on a fuel system.
- A P26Ax family token is not a complete scannable code.
Confirm the repair
- Use the specified monitor conditions; do not promise a fixed mileage until the light goes out.
Sources and scope
- Ford — Gasoline OBD System Operation Summary MY 2024–2025 Document: 2024-04-16 · 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
- Ford — OBD System Operation Summary, gasoline 2020–2023 update Document: 2023-10-23 · Research checked: 2026-11-01
- Subaru — 09-128-24R Document: 2024-11-14 · 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.