Toyota Highlander P0456: EVAP System – Small Leak

This is one of the most commonly encountered trouble codes for the Toyota Highlander Is the Code P0456. This is the trouble code that you get when you plug your Highlander in to a OBDII scanner. A P0456 code indicates that there may be a slight leakage in the evaporative exhaust control system. This code is often found with or related to P0420,P0441 and, very rarely, P0440.

Normally, P0456 does not pose a danger to your Highlander's driving ability. 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 Toyota Highlander, it is actually referring to the amount of pressure lost, and not the physical size of the leak. They can also be very tiny.

Toyota Highlander P0456 Definition

The universal OBDII code P0456 can be used to diagnose trouble codes. The code is universal, meaning that it will be the same regardless of the make and model of your vehicle (Highlander or otherwise). Technically, the code stands for:

System Leakage in the Smallest Detail – Evaporative Emission System

The EVAP captures any fuel vapor in the fuel tank. They are then sent to the engines intake for ignition. When there is a small leak in the Toyota Highlander’s EVAP system, it will throw the P0456 OBDII Code. If there is a large leak, it’ll throw P0455.

Toyota Highlander P0456 OBDII Code Symptoms

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

The fuel tank and fuel filler tubes 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 technology deals only with the fuel vapor but not how the engine runs in the Highlander.

Highlander P0456 Trouble Code Causes

P0456 can be triggered by many factors in your Toyota Highlander. If your Highlander 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.

• Hose of the Evap System– 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. It should be checked for tears or holes. 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. You will need to locate and take out a few clips.
• Fuel Tank Sending Unit– It is possible for the gasket that attaches the fuel sending unit to the gas tank to go bad. It can lower the tank pressure, which could throw out 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. You may not get the message but a P0456. This will save you time and 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- Toyota Highlander

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Toyota Highlander P0456. The most commonly used methods to diagnose this code are:

• The mechanic will check for any additional trouble 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 Take a look at 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.
• Monitor and check the pressure in your fuel tank.
• Following the inspections and repairs, the mechanic will conduct two more tests.
• 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

These are some of the more common Highlander P0456 fix:

• Replacing the 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 caps are the easiest to replace and the least costly.

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

You will need to be patient when trying to figure out why your Toyota Highlander is throwing the code P0456. We trust this helped. Please feel free to add anything below.

Are P0456 Serious Concerns?

While P0456 is not going to cause the Highlander’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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