P0455: EVAP System Gross Fuel Vapor Leak

What is P0455?

The code P0455 stands for “System Gross Leak Evaporative System Malfunction.” 

It’s a Diagnostic Trouble Code (DTC) that pops up when the EVAP system in your vehicle has been compromised, resulting in gasoline vapor escaping into the atmosphere. 

Here’s how this system works: 

The EVAP system consists of many components, including the fuel tank, gas cap, and charcoal canister (also called EVAP or vapor canister.) It prevents harmful fuel vapor from escaping your vehicle’s fuel system and being released into the environment. 

To ensure the EVAP system does its job, your car’s ECM monitors the fuel tank, gas cap, charcoal canister, purge valve solenoid, and canister valve vent solenoid. 

When you start your vehicle, the purge valve in the engine compartment opens and an intake vacuum absorbs the harmful vapor into the engine for efficient combustion. However, a large fuel vapor leak in the EVAP system will prevent vacuum creation. 

When the Leak Detection Pump (LDP) detects this gross leak during an EVAP test, the ECM generates a P0455 code.

Multiple factors could trigger an EVAP leak, causing the ECM to generate the DTC P0455 trouble code. You’ll also see the Check Engine Light (CEL) illuminated on your dashboard.

Note: If it’s a small leak, the ECM will pull up trouble code P0456.

Common Symptoms

In addition to a lit Check Engine Light, a few common indicators may accompany the P0455 error code. 

• A noticeable decrease in fuel economy
• A faint odor of fuel vapor
• Your vehicle may fail an emissions test 

Error code P0455 is commonly linked with codes P0440, P0441, and P0456. If you notice any of these on a scan tool, contact a mechanic to conduct an EVAP test.

P0455 Causes

Here are a few common causes that could trigger engine code P0455: 

• Malfunctioning gas cap: In most cases, a P0455 code is triggered due to a faulty, damaged, or missing gas cap (also called fuel cap or fuel filler cap). So, if your gas cap is loose, tightening it should resolve the code.
   
• Deteriorating fuel tank: Typically, a fuel tank can last for around 10 years. However, it can get cracked or punctured by road debris and physical impacts. Accumulation of dirt and debris within the fuel tank can also erode the filler neck, triggering the P0455 fault code.

• Worn-out purge valve or vent valve: A stuck-open canister purge valve or vent control valve can wear out or clog up due to accumulated dirt and debris. When this happens, it disrupts the purge flow within the EVAP system. The vehicle’s ECM triggers the engine code P0455, which illuminates the Check Engine Light (CEL).

• Damaged charcoal canister: The charcoal or vapor canister absorbs toxic carbon emissions from your car’s engine. However, overheating or overfilling your gas tank can degrade and clog your charcoal canister, causing a large EVAP leak.

• Defective or disconnected EVAP hose: The EVAP hose connects the fuel pump to the charcoal canister and then links the charcoal canister to the engine intake manifold. If there are any breaks or disconnections in the vacuum lines, it’ll cause an EVAP leak.

Can I Still Drive?

No, driving with a P0455 ending code isn’t recommended.

Although it doesn’t present any danger or drivability issues, it could affect the overall performance of your vehicle and even harm the environment by leaking harmful vapor into the atmosphere. 

So, if fault code P0455 turns up, it’s best to get your vehicle checked by a qualified technician as soon as possible.

Diagnosis

Diagnosing and resolving a large fuel vapor leak in the evaporative emission control system requires the right tools and technical know-how. 

So, if you’re unsure, you should get a certified technician to inspect your vehicle and perform a leak test.

But if you still wish to know how it’s done, here’s a general walkthrough of the entire troubleshooting process: 

• Your mechanic will diagnose a leaking evaporative emission system by checking for a faulty, missing, or loose gas cap.

• If the gas cap is ruled out as the cause of a large EVAP leak, they’ll use an OBD-II scan tool to check for and reset the diagnostic codes.

• If the error code persists, your mechanic will visually inspect all your EVAP system components, including the hose, EVAP canister, and fuel filler neck.

• Next, they’ll check for an EVAP system leak by conducting a smoke test with a smoke machine. Once the smoke machine fills the evaporative emission system components with smoke, they’ll observe where the smoke escapes to pinpoint the leak’s location.

• If no large leak is detected after the smoke test, they’ll check if the fuel tank pressure sensor has gone bad. They’ll also check if the purge valve solenoid or canister valve vent solenoid in the engine compartment has been compromised. 

Most people often instinctively replace the fuel cap once they get a P0455 code. However, that’s not always the solution. Code P0455 can be triggered due to issues such as a faulty or damaged fuel tank, purge valve solenoid, canister vent valve solenoid, or charcoal canister. 

So, it’s important to fully diagnose the root cause that triggers the code and then get the appropriate repairs.

Possible Repairs for P0455 & Costs

Once the EVAP code diagnosis is complete, your mechanic will need to repair or replace the faulty EVAP system components.

While a diagnostic check can cost you around $60-$100, the repair cost of the P0455 EVAP code can range from $20-$700. 

These costs can vary depending on the vehicle type, the parts that need repair or replacement, and the severity of the issue. 

Here’s an estimated cost breakdown of different EVAP repairs:

• Gas cap: $20-$60
• Vent valve or purge solenoid replacement: $150-$300
• Charcoal canister repair: $400-$510
• Fuel filler neck replacement: $60-$700