Honda Civic P0455: EVAP System → Leak Detected (Large)

This is one of the most commonly encountered trouble codes for the Honda Civic The Code P0455. This code is used to refer to the trouble code for your Civic that you get when it's plugged in to an OBD2 scanner. The number has to do to with the emissions system. The P0455 code indicates that the emission system is malfunctioning. Large leak In the evaporative emissions control system (EVAP). It is frequently found alongside, or closely related to, other codes like P0420/P0430, and even P0441.

P0455: EVAP System → Leak Detected (Large)

Your Civic's driveability is generally not affected by P0455. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though.

Honda Civic P0455 Definition

The universal OBDII code P0455 can be used to diagnose trouble codes. The code can be used regardless of the make and model of the vehicle. Technically, the code stands for:

System Gross Leak Evaporative Emission System

The EVAP system collects fuel vapor from fuel tanks and then sends it to the intake to ignite the engine in normal combustion. When there is a large leak in the Honda Civic’s EVAP system, it will throw the P0455 OBDII Code.

Honda Civic P0455 OBDII Symptoms

A P0455 Code will usually not cause any symptoms except the ones listed below. Smells like gas And the service engine soon light. The slightest drop in fuel economy may also be noticeable.

The fuel tank and fuel filler tubes should smell particularly strong.

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.

Causes of the Civic P0455 Trouble code

The P0455 trouble code can be triggered by many factors in Honda Civic. These are some of the more common issues that can trigger the P0455 trouble code in your Honda Civic.

• Hose for Evap System– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. The P0455 error code will be generated. It should be checked for tears or holes. This is usually the cause of code.
• Vapor Canister Purge Valve– One of the most common causes of the P0455 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.
• A Faulty Canister of Charcoal– The charcoal canister is often the cause of P0455.
• 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 P0455. 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. 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.

P0455 Diagnosis- Honda Civic

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Honda Civic P0455. The most commonly used methods to diagnose this code are:

• A mechanic will usually 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 P0455, he or she will usually Check out the EVAP System. These include the line and purge valve.
• 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.
• 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:

While the trouble code may state that there is a “large leak” in the EVAP system of your Honda Civic, the actual leak will most likely still look rather small. The “large” really is referring to how much pressure is being lost.

The Most Popular P0455 Fixes

Below are the top Civic P0455 fix options:

• Replacement of 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 caps are the easiest to replace and the least costly.

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

We wish you all the best in finding out why your Honda Civic is throwing the P0455 error code. We trust this helped. Please feel free to add anything below.

Do you consider P0455 to be a serious concern?

While P0455 is not going to cause the Civic’s engine to stop running, it should not be treated lightly. There could be fuel contamination. Check your tank regularly to make sure there is no fuel leaking. You should immediately take it in for repair or replacement.