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.
P0456EVAP System Small LeakP0456EVAP System Small Leak.If DTCP0456Evap System Small LeakP0456Evap System Small Leak(applies only to vehicles equipped with a CNG engine): Excess gasoline mode operation under normal operating conditions (switching to gasoline mode too often)View all · Manufacturer wording →
Manufacturer communications
27Original wording in English
RAM
Reported code forms P0456
Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ●…
RAM
Reported code forms P0456
Flash: Powertrain Control Module (PCM) Updates *Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): ●…
RAM
Reported code forms P0456
Customer complaint may include MIL-On/check engine lamp-on condition. Upon further inspection, a DTC for P0456-Small Leak Detected may be set in the PCM.
DODGE, JEEP, RAM
Reported code forms P0456
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…
RAM
Reported code forms P0456
Flash: Powertrain Control Module (PCM) Updates RAM 1500 PickupThis bulletin applies to vehicles within the following markets/countries: North America, APAC, EMEA and LATAM. This bulletin applies to vehicles equipped…
RAM
Reported code forms P0456
Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the PCM with the latest available software. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further…
Check vehicle applicability
8A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Ram | 1500 | 2022 |
| Ram | 1500 | 2021 |
| Ram | 1500 | 2020 |
| Ram | 1500 | 2019 |
| Ram | 1500 | 2016 |
| Ram | 1500 | 2015 |
| Ram | 1500 | 2014 |
| Ram | 1500 | 2013 |
Historical records · 1 · Historical vehicle association; OBD-II compatibility is not established by this record.
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) 13, 14 ·
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.