How to Fix Code P0456: Rescue Guide for Automotive Owners

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Car Engine

A check engine light and a few error codes are something that every car owner will deal with once in a while. One of these trouble codes, P0456, may be displayed on an OBD scanner right now, and you might not know where to start diagnosing. What does this code mean? How do I fix it? Do I need to pay a lot of money to solve this? 

Fear not, as all your questions should be answered in this article. We will be delving in and showing all the information you need about this specific error code. Are you ready to get rid of the trouble code P0456? Let’s get started!

What is Code P0456?

When the Engine Control Module (ECM) has identified a small leak, an OBD-II scanner will show error code P0456, which refers to an evaporative emission control system leak or malfunction. A car must be tested off-road and must fail twice for the ECM to recognize the problem and activate the code.

The Evaporative Emission Control System (EVAP), also known as the Fuel Vapor System, prevents gasoline vapors from escaping into the atmosphere. It is built up around a collection of valves, rubber hoses, and a charcoal canister designed to capture vapors as they accumulate. 

Symptoms of Code P0456

A small leak in the evaporative emission system isn't noticeable on a regular drive. The only sign your car will show is the Check Engine Light illuminating, and code P0456 is shown on an OBD scanner. However, in certain situations, some symptoms may appear, including:

  • Fuel efficiency has been reduced.
  • Vehicle emissions have increased.
  • The odor of gasoline.

Causes of P0456 Code

Since the EVAP is closed, the code P0456 is caused mainly by system components or any connections between them. The majority of the system is located at the bottom of the vehicle, making them vulnerable to physical damages and natural elements.

The following are some of the common causes of code P0456 that triggers the check engine light:

  • A gas cap that is loose or damaged
  • Connected or leaking hose for EVAP
  • A faulty purge volume control valve
  • Canister vent control valve that isn't working properly
  • Canister of charcoal leaks
  • Leaking fuel tank

How to Diagnose Error Code P0456?

The good news is that determining the cause of trouble code P0456 can be straightforward and not as tricky as other error codes. To guarantee that you fix the underlying problem (as opposed to merely ensuring the check engine light turns off) is to ensure that you diagnose thoroughly and not overlook anything.

In most cases, tightening the gas cap and clearing the fault codes will solve the problem. However, this is not always the case. So, if you tried these and nothing happened, try these steps.

Check for trouble code/s using an OBD Scanner

Plug in an OBD scanner to check all the possible error codes that might pop up. Check and note all the freeze-frame data that could help you determine when the leak had occurred. Look for any information concerning other codes, if found, to help you troubleshoot the problem.

Perform Visual Inspection

Thoroughly check the vapor purge valve system, including the valve itself and all the connected hoses and couplings. If you find any damaged or loose connections in the components, we suggest replacing these immediately.

Check for Leaks

Visually inspect for small leaks, evap leaks, vent leakage, and leaking charcoal canister. Attach an EVAP smoke machine to the EVAP system to see any leaks in the vent valve hose connectors around vacuum hoses or the fuel system. If any leaks are found, repair them immediately.

Check the Output

Detach the EVAP purge valve plug and use your scanner to perform an output assessment from the engine control module to the EVAP purge valve. Using a multimeter, measure the connection plug and ensure you have both a 12V+ and ground.

Send the 12V+ and ground to the purge control valve to test it. Check to see whether it is shutting and opening the air through it simultaneously. If broken, have it replaced immediately.

How to Fix Code P0456?

You may now fix the issue after diagnosing the problem and finding out the exact cause of this trouble code. However, if you are not skilled in automobile repairs, you should have a professional mechanic diagnose and repair any issues. But if you think you can do it your own, here are the possible fixes you can do:

Step-by-Step Guide to Replacing a Gas Cap

  • Before purchasing a new gas cap, consider whether or not you need a gas cap that locks to prevent a gas       thief from stealing your gas or just a standard gas cap. Please remember that if you install one of these          caps on your car, make sure to turn over the gas cap key to anyone that will put gas in it so they can                open the gas cap.
  • Remove a retention ring that holds the gas cap to your vehicle. Remove the retention ring that holds the       gas cap to your car. Use a pair of needle-nose pliers and simply slide one of its tips under the rin edge.           Close the pliers and pull the ring off the old cap, and put it over the new cap. Simply slide one of the                 pliers' tips under the ring edge, close the pliers and pull the ring off the old cap and over the new cap.
  • Check your engine light. It's normal for it to illuminate while changing the gas cap. Test drive your car for       a couple of miles to see if the light goes off. When the light shuts off, it means that the process was                 successful. 

Step-by-Step Guide to Replacing a Purge Valve

Removing the Faulty Purge Valve

  1. In removing the old purge valve, you first need to disconnect the EVAP engine vacuum pipe from the              EVAP canister purge pipe.
  2. Next, disconnect the engine compartment EVAP pipe at the EVAP canister purge valve.
  3. When the engine compartment s disconnected, move on to disconnecting the EVAP canister purge valve        harness.
  4. Finally, remove the EVAP canister purge valve.

Installing the New Purge Valve 

  1. You first need to ensure that the EVAP canister purge valve is installed into the bracket.
  2. Next, check all the electrical connectors for damage. If no damage has been found, connect to the EVAP          canister purge valve.
  3. After that, connect the engine compartment EVAP pipe to the EVAP canister purge valve.
  4. Lastly, connect the engine vacuum pipe to the EVAP canister purge valve.

Common Mistakes When Diagnosing the P0456 Code

People make mistakes when determining the exact cause of this issue because this error code is associated with many causes. So, what are the errors people make when diagnosing Code P0456?

  • Not checking if the gas cap is loose or damaged
  • Assuming that the cause is the purge volume control valve without verifying
  • Replacing the canister vent control valve even if it's working properly
  • Not checking the canister of charcoal for a leak.
  • Failure to check the fuel tank for leaking

P0456 Code FAQs

1. How serious Is the code P0456?

Anything that triggers the Check Engine Light to illuminate should be taken seriously as this means that the fuel vapor system is leaking. You should address the leak as soon as possible to avoid worsening the problem.

2. How long can I drive with an EVAP leak?

It is recommended not to drive your car for more than 30-50 miles with an EVAP leak.

3. How much is the repair cost of code P0456?

A minor leak problem associated with code P0456 will typically cost between $200 and $300, with most of that money going toward labor and diagnostics. Hoses and valves are frequently inexpensive to replace.

4. Where is the purge valve located?

The canister purge control valve is usually found in the engine bay on a hose that connects the intake to the canister. You can also find it close to the fuel tank.

5. How long do purge valves last?

The canister purge solenoid typically lasts the vehicle's life, but it does wear out from time to time. If the canister purge solenoid fails, the Check Engine light will illuminate, and your vehicle will need to be diagnosed and fixed as soon as you can. It can also trigger a failed emissions test.


If you’re experiencing code P0456, there are a couple of things you can do to try and fix the issue with the potential fixes we’ve outlined in this article. But if you are afraid to try these by yourself, we suggest reaching out to a professional car mechanic to diagnose and fix any issues for you.We hope this guide has helped you determine the cause and possible fixes for your car. Let us know what you think in the comment sections below. Thanks for reading!