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.
P0455EVAP System Large LeakManufacturer communications
6Original wording in English
DODGE, JEEP, RAM
Reported code forms P0455
Updated Fuel Filler Cap This bulletin involves updating the fuel filler cap with improved version. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further investigation the technician may…
JEEP
Reported code forms P0455
Customer complaint includes a Mil-on condition. Upon further investigation, one or more of the following fault codes may be set in the PCM: P0456 - EVAP System Small Leak P0455 - EVAP System Large Leak P04EC - EVAP…
JEEP
Reported code forms P0455
Customer complaint includes a Mil-on condition. Upon further investigation, one or more of the following fault codes may be set in the PCM: P0456 - EVAP System Small Leak P0455 - EVAP System Large Leak P04EC - EVAP…
DODGE, JEEP, RAM
Reported code forms P0455
Customer complains of the MIL lamp on. Technician observes DTC P0456 EVAP System Small Leak or P0455 EVAP System Large Leak detected set in PCM.
JEEP
Reported code forms P0455
Flash: Powertrain Diagnostic And System Enhancements This bulletin involves reprogramming the Powertrain Control Module (PCM) with the latest available software. Customers may experience a Malfunction Indicator Lamp…
CHRYSLER, DODGE, EAGLE, JEEP, PLYMOUTH
Reported code forms P0455
SUBJECT REGARDING MISDIAGNOSED LEAK DETECTION PUMP SYSTEMS WITH DIAGNOSTIC TROUBLE CODES P1494, P0442 P0455, OR P0456. *TT
Check vehicle applicability
7A 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.