Mercury Mountaineer P0455 Code Diagnosis

This is one of the most commonly encountered trouble codes for the Mercury Mountaineer Is the P0455 Code. This code is a trouble number. It's the one you get when you connect your Mountaineer to an OBDII scanner. The trouble code P0455 indicates that there are a Large leak In the evaporative emissions control system. It is frequently found in conjunction with other codes such as P0420 or P0441.

Normally, P0455 will not cause any immediate damage to your Mountaineer's driveability. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though. It's often associated with P0442. More information is available at Mercury Mountaineer OBDII Code P0442.

Mercury Mountaineer P0455 Definition

The universal OBDII code P0455 can be used to diagnose any problem. It means that no matter what make or model vehicle you have, this code will always mean the same (Mountaineer). Technically the code is:

System Gross Leak – Evaporative Emission System

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

Mercury Mountaineer P0455 OBDII Code 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.

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

Fuel vapors are dealt with directly by the EVAP. If these vapors are leaking from the system, you’ll often smell them faintly while operating the vehicle.

Mountaineer P0455 Trouble Code Causes

You can have the Mercury Mountaineer's P0455 trouble code trigger for many reasons. These are some of the more common issues that can trigger the P0455 trouble code in your Mercury Mountaineer.

• Hose for Evap System– The hose that carries the fuel vapor from the fuel tank to the intake manifold can begin to leak. This can lead to the P0455 code. 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 P0455 code is the vapor canister purge valve. It’s really easy to replace. You will need to locate and take out a few clips.
• 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. 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.

P0455 Mercury Mountaineer Diagnosis

The mechanic will have a lot of different tools at his disposal in order to determine the cause of your Mercury Mountaineer P0455. These are some of the common diagnostics that can be done for the code

• A mechanic will usually 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 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.
• 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:

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

Commonly Used P0455 Fixes

These are some of the most popular Mountaineer P0455 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.

We wish you all the best in your search for the reason that Mercury Mountaineer threw the code P0455. We trust this helped. You can add any additional information by leaving a comment.

Are P0455 Serious Concerns?

While P0455 is not going to cause the Mountaineer’s engine to stop running, it should not be treated lightly. There could be fuel contamination. 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.