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.
Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P0455EVAPORATIVE SYSTEM GROSS LEAK DETECTEDManufacturer communications
3Original wording in English
FORD
Reported code forms P0455
SOME VEHICLES EQUIPPED WITH A VAPOR MANAGE VALVE (VMV) MAY EXHIBIT A DIAGNOSTIC TROUBLE CODE P0455 (EVAPORATIVE SYSTEM GROSS LEAK DETECTED). *TT
FORD
Reported code forms P0455
SOME VEHICLES MAY EXHIBIT A MALFUNCTION INDICATOR LAMP ILLUMINATED WITH DIAGNOSTIC TROUBLE CODES P0455, P0456, P0457, P0442, P1442, P1443, P1450 OR P1455 FOR THE EVAPORATIVE EMISSION SYSTEM. *TT
FORD, LINCOLN, MERCURY
Reported code forms P0455
SOME VEHICLES MAY EXHIBIT A DIAGNOSTIC TROUBLE CODE P0455 CAUSED BY AN EVAPORATIVE SYSTEM LEAK. *TT
Check vehicle applicability
5A 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.
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 ·
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.