Reference meaning
What does this code mean?
P0442 describes a small leak, P0455 a large leak and P0456 a very small leak. Check the correct fuel-cap seal where fitted, hoses, valves and the manufacturer's leak-test procedure. A loose cap is one possibility, not the only cause. Do not use compressed air or improvised flame tests around fuel vapour.
Sources and interpretation [1]
A code identifies a detected condition, not a part that must automatically be replaced.
Narrow by vehicle
A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Scan worksheet →Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P0455EVAP System Large Leak
P0455EVAP System Large Leak
P0455GROSS LEAK DETECTED
Manufacturer communications
185Original wording in English
ACURA
Service Bulletin - The factory fuel fill pipe assembly may not have been manufactured to specification. As a result, small contamination particles inside the fuel fill neck may prevent the primary shut-off valve flap seal from sealing properly. This may result in a fuel smell from the fuel fill neck area and may cause DTC P0455 …
ACURA
Service Bulletin - The factory fuel fill pipe assembly may not have been manufactured to specification. As a result, small contamination particles inside the fuel fill neck may prevent the primary shut-off valve flap seal from sealing properly. This may result in a fuel smell from the fuel fill neck area and may cause DTC P0455 …
ACURA
Dealer Message - The fuel fill pipe assembly may not have been manufactured to specification. As a result, small contamination particles inside the fuel fill neck may prevent the primary shut-off valve flap seal from sealing, resulting in fuel smell from the fuel fill neck area and may cause DTC P0455 or P0456 (EVAP system leak …
FORD
*This article supersedes TSB 24-2199 to add the rear half shaft seals to the TSB parts list. Some of the vehicles listed in the model statement above may exhibit one of the following conditions: *Fuel tank not filling up beyond half-full *Hard to start *Stalls upon restart after refueling *A malfunction indicator lamp (MIL) with…
Check vehicle applicability
3274A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Sources and interpretation
These explanations are editorial summaries of the linked manufacturer material. PDF page numbers count from the first file page. Original publications are in English; translations are reference aids. A cited edition is not a claim that it is the manufacturer's latest instruction.
- 2024–2025 MY OBD System Operation Summary for Gasoline Engines ↗
Ford Motor Company · PDF page(s) 11, 12 · 2024-04-16
Source check date · 2026-10-27
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.