GMC Sierra P0455: EVAP System Large Leak Detected Diagnosis

This is one of the most commonly encountered trouble codes for the GMC Sierra The Code P0455. The trouble code is the number given when you connect your Sierra to an OBDII scanner. The trouble code P0455 indicates that the problem is serious. Leakage large In the evaporative emissions control system. It is frequently found in conjunction with other codes such as P0420 or P0441.

P0455: System Gross Leak Evaporative Emission

Your Sierra Sierra is usually not at risk from P0455. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though. It may also be accompanied with P0442. For more information, see GMC Sierra P0442 OBDII code.

GMC Sierra P0455 Definition

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

System Gross Leak 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 large leak in the GMC Sierra’s EVAP system, it will throw the P0455 OBDII Code.

GMC Sierra P0455 OBDII Code Symptoms

A P0455 Code will usually not cause any symptoms except the ones listed below. The smell of gas And the service engine soon light. It is possible to notice a slight dip in fuel economy.

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.

Sierra P0455 Trouble Code Causes

Many things can trigger the P0455 code in GMC Sierra. The most frequent problems that trigger this code are:

• Hose of the 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. 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 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. It may be worth your time to get that message and a P0455 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.

P0455 Diagnosis - GMC Sierra

To diagnose the problem with your GMC Sierra's P0455, a mechanic can use a variety of tools. These are some of the common diagnostics that can be done for the code

• The mechanic will check to make sure there are no other 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.
• Once the mechanic has determined the trouble codes associated with P0455, he or she will usually Take a look at the EVAP system. It includes the purge valve and line as well as the canister.
• 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.
• 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 GMC Sierra, 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 Sierra P0455 fix options:

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

It is best to begin with the gas cap, and then work your way up to the fuel tanks. The gas cap is the most difficult and cost-effective item to replace.

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

You will need to find the cause of your GMC Sierra throwing the P0455 code. We trust this helped. Please feel free to add anything below.

Are P0455 Serious Concerns?

While P0455 is not going to cause the Sierra’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.