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P0455 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.

Definition

P0455-`System Gross Leak Evaporative Emission

Meaning

Typically, we see this trouble code alongside the P0440, an indicator that there is a problem with your vehicle’s Fuel Evaporative Emission System (FEES). The P0455 code specifically indicates a large leak in the system, not a fuel leak, but one in the vapor recovery system.

A 0455 trouble code indicates a large leak in the vapor recovery system as opposed to the fuel system in general. The good news is your vehicle is likely not leaking highly flammable and costly gasoline. The bad news is that now you need to track down the source of the leak.

Causes

Tracking down a leak in any vehicle system can be a tricky proposition. Here are a few common causes to help you narrow it down:

The most common cause we see for a P0455 is a fuel filler cap issue. Usually, this error code means the gas cap is missing,  incorrectly installed, not sealing properly when tightened down, or there may be damage to the top of the filler neck. Check these probable causes first.

Your next best bet for resolving this trouble code involves checking your hoses. Breather system hoses have a tendency to crack with age, and the connecting hose on the filler neck that feeds fuel to the gas tank is often the culprit. Make sure the seals are tight and that there are no obvious signs of wear or cracking.

Every vehicle’s EES has a purge valve that regulates system pressure. This isn’t a DIY fix though, and you should have the EES purge valve checked by a qualified automotive technician.

Some Vehicles us a charcoal filter on their EES, and like hoses it needs to be checked for cracks, damage, or leaks. Again, checking for worn out or broken parts should be the first step in diagnosing this issue.

Finally, the fuel tank itself may be leaking (a serious problem), or the gasket where the fuel level sensor, pressure sensor, and fuel pick attach to the tank may have a leak. You’ll need to check a vehicle specific maintenance manual or manufacturer’s system diagram to properly verify each component's location and check for damage. Above all, keep in mind that even if you are pulling a P0455 trouble code, the leak in the system may be small.

Symptoms

Your check engine light will come on first, but generally you won’t notice any difference in drivability. You may smell gasoline around the filler cap or near the gas tank even when the filler cap is in place. Sometimes the odor of gasoline will also be detectable around the evaporative fuel lines to the engine’s fuel intake.

Since you should be checking the filler cap, hose and gas tank as part of your troubleshooting process, you may or may not smell gasoline around any part of the fuel system leading from the tank to the engine.

Diagnosis

An important component of resolving any trouble code is following an effective diagnostic process. If you don’t take diagnosis step-by-step, you may miss the root cause and find yourself spending time and money replacing or repairing parts that aren’t actually causing the problem. Here’s the troubleshooting process our technicians use:

  • Hook up your OBD-II scanner and check for code P0455. Check to make sure the filler cap is tightened down properly, and then reset all OBD-II fault codes and take a rest drive to verify if the code reoccurs. If it does, watch the live date on your OBD-II scanner while the vehicle is running.
  • If your vehicle codes P0455 again, do a visual inspection around the filler cap, hose and gas tank to determine any obvious leaks.
  • Can’t find any obvious leaks? If you have access to one, use a smoke test system to try and spot the leak.
  • If your fuel system passes the smoke test, then it’s likely you have a sensor issue.  You will need to run a diagnostic on the sensor according to the manufacturer's instructions because each system differs slightly from vehicle to vehicle.

Common mistakes

It is critically important to make sure your filler cap is properly tightened before you start swapping out expensive fuel system components. Don’t run the smoke test until you have completed this very simple yet important step. The issue may be a cracked EVAP hose that can be easily and quickly exchanged for a minimal cost.

How serious is this?

When your OBD-II scanner is reading P0455, you probably won’t even notice a difference in how it drives and handles. That being said, if you can smell a strong odor of gasoline even when your gas cap is down tight, take your vehicle to a qualified mechanic right away..

Fuel system leaks can cause a significant drop in fuel economy depending on the circumstances and seriousness of the leak, so it’s best to get your vehicle to the shop right away. Sometimes the technician can’t find a leak in the system, so they will reset the codes and retest.

Additionally, make sure you have at least half to three-quarters of a tank of gasoline in your vehicle for optimal testing. Furthermore, if your check engine light comes on immediately at start up, the OBD-II system can be reset and the vehicle will operate normally.

What repairs can fix the code?

Here are the typical repairs to resolve a P0455 trouble code:

  • Replace the gas cap if it won’t seal or tighten properly (cheap, inexpensive fix)
  • Replace the fuel filler neck due to damage or if it won’t seal even with a new filler cap (somewhat expensive and labor intensive)
  • Repair or replace any leaking hoses (usually a quick and inexpensive fix)

Related codes

P0440 as noted above.

Conclusion

Smelling a strong odor of gasoline emanating from your car is never a good thing. Fuel leaks aren’t usually significant or difficult to repair, but it is important to resolve them quickly. Obviously, leaking gasoline creates hazardous conditions that can lead to significant vehicle property damage, not to mention the environmental impacts. If you smell gas and your check engine light is on, get that vehicle in the shop ASAP.