Chevy Express P0455: EVAP Large Leak Diagnosis

This is one of the most commonly encountered trouble codes for the Chevy Express The Code P0455. The trouble code refers to a number you receive when your Express is plugged into an OBDII scanner. The trouble code P0455 indicates that the problem is serious. Leakage large It is part of the evaporative emission controller system. It is frequently found in conjunction with other codes such as P0421, P0441 and P0440.

P0455: System Gross Leak Evaporative Emission

Normally, P0455 does not pose a danger to the driving ability of your Express. Certainly anytime the service engine soon light is on, it’s good to deal with it as soon as possible though. P0442 is usually accompanied. More information is available at Chevy Express OBDII Code P0442.

Chevy Express Definition P0455

P0455 refers to a general OBDII trouble code. 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 Chevy Express’s EVAP system, it will throw the P0455 OBDII Code.

Chevy Express OBDII code Symptoms P0455

The P0455 code is usually not accompanied with any other symptoms than those listed. The smell of gas The service engine soon light. The slightest drop in fuel economy may also be noticeable.

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

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.

Express P0455 Trouble code Causes

Many things can trigger the P0455 code in Chevy Express. These are some of the more common issues that can trigger the P0455 trouble code in your Chevy Express:

• Evap Hose– 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. 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. You will need to locate and take out a few clips.
• The Faulty Charcoal Caister– 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. 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. 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.

Chevy Express - P0455 Diagnoses

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

• A 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 P0455. 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.
• 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 Chevy Express, the actual leak will most likely still look rather small. The “large” really is referring to how much pressure is being lost.

Most common P0455 fixes

Below are the top Express P0455 solutions:

• Replacement of gas cap
• Replacement for EVAP Line
• Replace charcoal canister
• Change 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 test your gas tank.

You will need to solve the problem quickly. This information is hoped to be helpful. Please feel free to add anything below.

Are P0455 Serious Concerns?

While P0455 is not going to cause the Express’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.