Nissan Altima P0456: EVAP System – Small Leak

The most frequent trouble code with the Nissan Altima The Code P0456. This is the trouble code that you get when your Altima plugs into a OBDII scanner. The code P0456 indicates that the evaporative emissions control system has a tiny leak. It is sometimes found along with other codes such as P0440, P0441, or very frequently P0440.

The P0456 problem is not usually a threat to your Altima'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 Altima, 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 Altima P0456 Definition

P0456 stands for a universal OBDII Trouble Code. It means that no matter what make or model vehicle you have, this code will always mean the exact same thing. Technically, the code stands for:

Installation Leakage of Small Size – Evaporative Emission System

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

Nissan Altima P0456 OBDII Code Symptoms

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

Particular attention should be paid to the smell of fuel near the fuel filler tube or tank.

The EVAP process deals with fuel vapors directly. 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 technology deals only with the fuel vapor but not the operation of your Altima engine.

Altima Trouble Code P0456

P0456 can be triggered by many factors in your Nissan Altima. If your Altima 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.

Below are the top most probable problems that could throw the code. These were listed alphabetically, in some order.

• Evap Hose– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. This can lead to the code P0456. You should look for a hole or a tear in the code. This is the leading cause of 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. The gasket may dry out especially if the vehicle is in dry conditions. When it dries out, the fuel tank can’t hold pressure anymore.

P0456 Diagnosis- Nissan Altima

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Nissan Altima P0456. These are some of the common diagnostics that can be done for the code

• The mechanic will usually check for any additional trouble codes. A mechanic will usually check for additional trouble codes to help diagnose the problem. 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.
• The mechanic will normally determine what trouble codes are associated with P0456. Take a look at the EVAP system. It includes the purge valve and line as well as the canister.
• A mechanic will examine the gas cap and verify that it is able to withstand high pressure. 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.
• Monitor and check the pressure in your fuel tank.
• 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:

Most common P0456 fixes

Below are the top Altima P0456 solutions:

• Replacing the gas cap
• Replacing EVAP lines
• 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 most easily and cheaply.

Here’s a great video on How to test your gas tank.

It's a good idea to try and figure out why your Nissan Altima is throwing the code P0456. We trust this helped. You can add any additional information by leaving a comment.

Are P0456 Serious Concerns?

While P0456 is not going to cause the Altima’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.

Please leave comments below if you have any suggestions. Thanks!