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. 

The EVAP system comprises many components, including the fuel tank, gas cap, and charcoal canister (also called EVAP canister.) It prevents harmful fuel vapor from escaping into the environment. To ensure the EVAP system is doing its job, your car’s ECM monitors the fuel tank, gas cap, charcoal canister, purge valve solenoid, and canister vent valve solenoid. 

The purge valve opens when you start your vehicle, and an intake vacuum absorbs the harmful vapor into the engine for efficient combustion. However, a leak in the EVAP system would prevent vacuum creation. So, if the leak detection pump (LDP) detects a gross leak, the ECM generates code P0455.

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 illuminated on your dashboard in this event.

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

Common symptoms

Here are a few common indicators that may accompany the P0455 fault code: 

• Your dashboard Check Engine Light is illuminated
• There’s a noticeable decrease in the fuel economy
• There’s a faint odor of fuel vapor

Error code P0455 is commonly linked with codes P0440, P0441, and P0456. So if you notice any of these, contact a mechanic to get your car checked.

Can I still drive?

While the P0455 code doesn’t present any danger or drivability issues, it could gradually affect the overall performance of your vehicle while leaking harmful vapor into the environment. 

So, if fault code P0455 turns up, it’s best to have your vehicle checked by a qualified technician at the earliest.

P0455 causes

Here’s a look at factors that could trigger P0455: 

• Malfunctioning gas cap: In most cases, code P0455 is triggered due to a faulty, damaged, or missing gas cap (also called fuel cap or fuel filler cap). So, if you notice your gas cap popping loose after being tightened, you may need to get it replaced. 
• Deteriorating fuel tank: Typically, a fuel tank lasts 15 to 20 years but can get cracked or punctured by road debris or physical damage. 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 purge valve or vent control valve can wear out or clog up due to an accumulation of dirt and debris. When this happens, the vehicle ECM will trigger the code P0455, and the Check Engine Light illuminates.
• Damaged charcoal canister: The charcoal canister absorbs toxic carbon emissions produced by your car’s engine. However, overheating or overfilling your gas tank can degrade and clog your charcoal canister, causing an EVAP system leak.
• Defective or disconnected EVAP hose: The EVAP hose creates a vacuum line from the fuel pump to the charcoal canister, then the charcoal canister to the engine intake manifold. If there are any breaks or disconnections in the lines, it’ll cause an EVAP leak.

Diagnosis

Diagnosing and resolving a large leak in the evaporative emission system requires the right tools and technical know-how. So if you’re unsure, you should get a certified technician to inspect your vehicle.

That being said, here’s a general walkthrough of the entire diagnostic process: 

• Your mechanic will begin diagnosing a leaking evaporative emission system by checking for a faulty, missing, or loose gas cap. 
• If the gas cap shows no sign of a gross leak, they’ll use an OBDII scanner to check and reset the diagnostic codes.
• If the fault code persists, your mechanic will visually inspect all your EVAP system components, including the hose, EVAP canister, and filler neck. 
• Next, your mechanic will check for an EVAP system leak by conducting a smoke test. To perform the smoke test, your mechanic will fill the evaporative emission system components with smoke and then check for signs of a leak.  
• If there’s still no gross leak detected, they’ll check if the pressure sensor, including the purge valve solenoid or canister vent valve solenoid, has been compromised. 

Most people often instinctively replace the fuel cap once they get code P0455. However, that’s not always the correct solution.

Trouble code P0455 can be triggered due to several issues, including 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 before conducting appropriate repairs

Possible repairs for P0455 & Costs

Once the fault code P0455 diagnosis is complete, your mechanic will need to repair or replace the faulty EVAP system component.

Depending on the vehicle type and severity of the issue, the repair cost of fault code P0455 ranges from $25–$600.

Here’s an estimated cost breakdown:

• Diagnosis: $100
• New gas cap: $25
• Vent valve or purge solenoid replacement: $200–$300
• Charcoal canister repair: $400–$600
• Filler neck replacement: $300–$400