P0456 - How To Repair: Meaning, Causes, Symptoms, Fixes

P0456 Code Definition

Evaporative Emission System Leak Detected (very small leak)

What Does the Engine Code P0456 Mean?

The character "P" in the first position of diagnostic trouble code (DTC) represents the powertrain system (engine and transmission), "0" in the second position means that this is a generic OBD-II (OBD2) DTC. The "4" in the third character position in a DTC indicates that the auxiliary emission controls malfunction has been detected. The last two characters "56" are DTC numbers. OBD2 Diagnostic Trouble Code P0456 indicates that a leak in the evaporative (EVAP) emission system has been detected. The evaporative emission control (EVAP) system helps reduce fuel-system vapor leaks into the atmosphere. Through hoses and tubes, an EVAP system routes fuel fumes from the fuel tank into a charcoal canister storage container and by switching valves and solenoids, re-routes them back to the engine, where they are burned off in the combustion process. If a sensor has noted a fuel vapor leak or lack of purge flow in the EVAP control system, Diagnostic Trouble Code P0456 is generated and stored in the Powertrain Control Module (PCM).

What Is the Cause of P0456?

While the most common cause of the P0456 code is a missing or loose gas cap, P0456 can also be caused by other issues:

A defective plug/cable on a valve

A defective fuse/voltage supply

Disconnect or clogged hoses

A defective tank vent valve

A damaged vapor canister

What Are the Symptoms of Code P0456?

The main symptom to the driver is the illumination of the check engine light (CEL), also called malfunction indicator lamp (MIL). The driver very likely will not notice any drivability problems, although there may be the following symptoms:

A fuel smell when the car is left in a closed space (e.g. garage)

A minor increase in fuel consumption

Which Tools Are Needed To Diagnose P0456?

To find out more about the P0456 code that is generated and stored in the Powertrain Control Module (PCM) of your car, the only tool you need is the Carly Universal OBD2 Scanner, which works for all car brands in the world with an OBD2 port. Carly is a revolutionary solution that allows you to access your car’s data with your phone and translates this information into powerful insights, predictions, and possibilities. This saves you trouble, time, and money.

How To Diagnose and Clear the Code P0456?

Performing a diagnostics check with a diagnostic scanner helps you identify a particular problem area that is outside the normal range and shows where a fault might be occurring. This helps you to detect errors before they cause more damage to your vehicle. In comparison to generic OBD devices that only provide OBD-level engine-related data, Carly can run advanced manufacturer-level diagnostics, check all your ECUs in your car (like ABS, airbag, multimedia) and get deeper insights. You can find additional information about the trouble code and understand the severity of the problem. With the new Smart Mechanic feature, you get additional professional insights and tips from expert mechanics. You are able to check components and their mechanics, find detailed repair tips, and learn about potential future damage. After you have fixed the problem you can easily clear the fault codes with Carly, too. Also, the diagnostic results are safely stored inside the app or as convenient PDF reports you can share with your friends or a mechanic.

Common Mistakes When Diagnosing the P0456 Code

The most common mistake is to look and try to fix each individual OBD2 code without having a holistic approach. Understanding the interrelationship of OBD-II (OBD2) systems is crucial to determining the root cause of the issue and finding the right solution. For example, a very common cause of the P0456 code is a loose gas cap. In some cases simply tightening a gas cap may already resolve the issue, while many instead people rush immediately to replace a specific component in the EVAP system.

How Serious Is Code P0456?

While it is common for a driver to experience no driveability issues when the P0456 trouble code is present, driving with this code is increasing the negative impact of your emissions on the environment. Therefore, it is recommended to have this code properly diagnosed and the issue solved as soon as possible.

How to Fix the P0456 Code?

Depending on the root cause of the problem, one or more of the following repairs can fix the P0456 code:

First, inspect the fuel cap to see how well it fits onto the fuel tank filler neck. If the cap doesn't tighten or seal, replace the gas cap or fuel tank filler neck.

Then, check the cables and connectors of the tank vent valve. To do this, disconnect the connector from the tank ventilation valve. Check whether the pins in the connector and component are in order and if there is oxidation. At the same time, you can check whether the valve is damaged externally.

The fuse of the tank vent valve or the voltage supply at the plug of the tank vent valve should be checked. The nominal value should be equal to on-board voltage (9-14V). If the voltage is 0V and the fuse is OK, the wiring harness must be checked.

Then pull off the plastic hoses on the tank vent valve and check whether the hoses are clean inside. Sand deposits can occur in the hoses. If this is the case, the activated carbon filter is defective.

If all sources of error have been ruled out, replace the tank vent valve.

Learn More about the P0456 Code

The EVAP system captures evaporated components of the fuel and feeds the components into the combustion process. On the one hand, it prevents hydrocarbons from escaping into the environment. The fuel expands and thus promotes evaporation. However, at constant pressure and temperature, evaporation decreases over time, because only the light hydrocarbons evaporate. On the other hand, the EVAP system avoids a vacuum in the tank when the fuel is removed. Therefore, a ventilation system is installed at the rear of the tank.

What is an EVAP valve and its function?

The EVAP valve controls the regeneration of the activated carbon filter by purging air. The purged air is drawn through the activated carbon filter and hydrocarbon (HC) is enriched. The amount of enrichment depends on the HC loading of the activated carbon. The purged air is then fed to the engine for combustion.

*Every car is unique. The Carly Features that your car supports depend on the model, build year, hardware, and software in the car. Plug the scanner in the OBD2 port, connect to the app, run your first diagnostics, and check which features are available for your car. Also, keep in mind that any information provided on this website is for informational purposes only and should be used at your own risk. Mycarly.com is not responsible for any errors or omissions, or for the results stemming from the use of this information.