Nissan Maxima P0456: EVAP System – Small Leak

The most frequent trouble code with the Nissan Maxima Is the Code P0456. The trouble code refers to a number you receive when your Maxima is plugged into a OBDII scanner. A P0456 code indicates that there may be a slight leakage in the evaporative exhaust control system. It is sometimes found along with other codes such as P0441 or P0420.

The P0456 issue is not usually a threat to your Maxima's driveability. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible.

While the trouble code may state that there is a “small leak” in the EVAP system of your Nissan Maxima, it is actually referring to the amount of pressure lost, and not the physical size of the leak. This can happen in very small amounts.

Nissan Maxima P0456 Definition

P0456 stands for a universal OBDII Trouble Code. The code can be used regardless of the make and model of the vehicle. It stands for the following:

System Leakage of Small Size – Evaporative Emission System

The EVAP system collects fuel vapor from your fuel tank, and then sends it to the intake to ignite the engine in normal combustion. When there is a small leak in the Nissan Maxima’s EVAP system, it will throw the P0456 OBDII Code. If there is a large leak, it’ll throw P0455.

Nissan Maxima P0456 OBDII Code Symptoms

The P0456 code is usually not accompanied with any other symptoms than those listed. Smells like gas And the service engine soon light.

The fuel tank or fuel filler tube should smell particularly strong.

The EVAP system is responsible for fuel vapors. If these vapors are leaking from the system, you’ll often smell them faintly while operating the vehicle. But, it won’t affect the way the engine itself runs. The EVAP system is for fuel vapor and does not affect the operation of your Maxima.

Maxima's P0456 Trouble Code Reasons

P0456 can be triggered by many factors in your Nissan Maxima. If your Maxima has warned you at all in the last few months that the fuel cap was off when it wasn’t, then replacing it would be a great first step.

These are some of the most frequent problems that can throw off the code. They're listed in alphabetical order, from the most likely to the least.

• Evap Hose– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. The P0456 error code will be generated. You should look for a hole or a tear in the code. This is the main problem that can cause the code.
• Vapor Canister Purge Valve– One of the most common causes of the P0456 code is the vapor canister purge valve. It’s really easy to replace. There are some clips you will need to look for and then remove.
• Fuel Tank Sending Unit– It is possible for the gasket that attaches the fuel sending unit to the gas tank to go bad. This could cause a drop in tank pressure which can throw off the code.
• Fuel Cap– A bad fuel cap can cause the code to be thrown for sure. Often, you’ll get a message informing you that the fuel cap is off even when it is on. It may be worth your time to get that message and a P0456 to ensure you don't waste any money.
• Fuel Filler Neck– There is often a gasket where the fuel filler neck connects with the gas tank. It is possible for this gasket to dry, particularly if vehicles spend a lot of time in dry environments. When it dries out, the fuel tank can’t hold pressure anymore.

P0456 Diagnosis- Nissan Maxima

To diagnose the problem with your Nissan Maxima's P0456, a mechanic can use a variety of tools. These are some of the common diagnostics that can be done for the code

• It is common for the mechanic to check for additional codes. It is easier to diagnose problems if there are more codes. That’s because when they appear together in certain combinations, there will often only be only a few conditions that will throw any combination of codes at one time.
• Once the mechanic has determined the trouble codes associated with P0456, he or she will usually Check out the EVAP System. These include the line and purge valve.
• To ensure that the cap can withstand pressure, the mechanic will check it. If you are getting a warning that your gas cap is off, even when it’s on, replacing it will more than likely clear this code.
• Monitoring and checking the fuel tank pressure is a must.
• The mechanic will then perform the following tests after completing the above-mentioned checks:
• A smoke test, and they’ll use a scan tool to confirm that the EVAP solenoids and valves are operating properly.

Here’s a pretty good video on diagnosing these leaks from Scotty Kilmer, if you are interested:

The Most Popular P0456 Fixes

Below are the top Maxima P0456 solutions:

• Replacement of gas cap
• Replacement for EVAP Line
• Replace charcoal canister
• Replacing the fuel tank

You should start with the gas caps and move on to the fuel tanks. This is because the gas cap can be replaced the easiest and most cost-effectively.

Here’s a great video on How to check your gas cap.

We wish you all the best in finding out why your Nissan Maxima is throwing the P0456 code. This should help. Please feel free to add anything below.

Do you consider P0456 to be a serious concern?

While P0456 is not going to cause the Maxima’s engine to stop running, it should not be treated lightly. Fuel leaks could be a problem. You should pay extra attention to the level of your fuel tank and ensure that you're not leaking fuel. You should immediately take it in for repair or replacement.

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