P0456 Code

What Is a P0456 Trouble Code?

As a vehicle owner, it’s bound to happen eventually — you’re driving down the road, thinking about anything but your car’s performance, when the check engine light suddenly illuminates. 

The appearance of this light can be worrisome. You won’t know what it means until you connect a hand-held scanner to your vehicle’s onboard diagnostic (OBD) system to obtain a diagnostic trouble code (DTC). Many auto parts shops and mechanics provide this service for free.

A DTC enables you or a mechanic to pinpoint the issue that triggered the check engine light. There are thousands of DTCs, each indicating a specific problem with the engine or another vehicle part or component. If the scan uncovers a P0456 code, it’s identifying a small leak in the emissions system. 

What Does a P0456 Mean?

A P0456 check engine code indicates a specific condition — “Evaporative Emissions System Small Leak Detected.” Your vehicle contains a complex evaporative emissions system, which helps prevent the leakage of harmful fuel vapors into the environment. This component has a specially designed charcoal filter that diverts the vapors into the engine while the auto is running. 

Even a small leak in the complex evaporative emissions system will trigger a P0456 code in a Jeep, Chrysler, Toyota or other OBD-equipped vehicle. The onboard electronic control module (ECM) must detect the leak during two separate testing cycles before issuing the code and causing the warning light to illuminate. 


What Are the Causes of the P0456 Code?

The ECM will signal the system’s closing via the purge control valve and activate the evaporative vacuum pump for testing and monitoring. After detecting a small leak, the ECM will store the code. If a subsequent test indicates a second leak, the ECM will activate the warning light.

A problem with any of the system components can trigger the code, including:

  • A cracked or loose gas cap that allows fuel vapors to escape.
  • Smaller leaks inside the fuel tank. 
  • Decayed, cut or otherwise damaged or inoperative fuel lines.
  • Damage to the purge solenoid.
  • A cracked charcoal filter.


What Are the Signs of the P0456 Code?

You probably won’t notice any difference in your vehicle’s performance when you have a small leak in the evaporative emissions system. The first sign of trouble will likely be the illumination of the check engine light. If you keep driving the auto without confirming the code and correcting the issue, you may eventually detect a slight decrease in fuel economy or a faint smell of burning gas. 


How to Check the P0456 Code

A mechanic will conduct several steps to ensure an accurate diagnosis of a P0456 code-related issue, including:

  • Scanning and documenting the code in the ECM and pinpointing when the failure occurred by observing and verifying the stored information.
  • Evaluating the state of the system components, including the valve and vent valve hose connections, for loose or improper fitting.
  • Assessing the valve to determine whether it can hold a vacuum while in use.
  • Examining the vent for dirt clogs or other obstructions that could prevent the valve from maintaining a tight seal.
  • Conducting a comprehensive assessment of the fuel vapor system to identify the origin of leakage. This assessment includes checking components such as the fuel cap and applying the test vapor port.


Fixing a P0456 Code in Your Jeep, Toyota, Ford or Other Vehicle

After locating the cause of the leak, it’s time to fix the targeted area of the emissions evaporation system. The cost to fix a P0456 issue can vary depending on the problem. The issue may stem from a broken or rotted hose, which often results from prolonged exposure to extreme weather conditions. In this case, you’ll need to replace the damaged section. This project can present a good opportunity to upgrade all the hoses, especially if you notice signs of wear. 

If you’ve determined that the P0456 code results from an air leak, you’ll likely need to replace the purge solenoid, filter canister or both components. While these are relatively expensive solutions, they’re necessary for pressurizing the emissions evaporation system. 

Have you traced the cause of a P0456 check engine code to a potential gas cap issue? Check the gas for cracks or other damage and replace it if necessary. If this component appears intact, make sure it is sealed properly and check to see if adjusting the seal turns off the light. 


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