P0455 Code: Causes, Troubleshooting, and Repair

As a car enthusiast or a DIY mechanic, you may have come across a P0455 code during a diagnostic scan. It's important to understand what this code means and how to address the underlying issue to keep your vehicle running smoothly. In this comprehensive guide, we'll explain the P0455 code, its common causes, and provide troubleshooting and repair tips to help you resolve the issue.

What is the P0455 Code?

The P0455 code is an OBD-II (On-Board Diagnostics) trouble code that indicates a large leak in the Evaporative Emission Control (EVAP) system. The EVAP system is responsible for controlling the release of fuel vapors from your vehicle's fuel tank into the atmosphere. When functioning properly, the system captures these vapors and sends them to the engine to be burned during combustion. Read this article to learn more about the EVAP System: What is the EVAP System and How Does it Work?

A P0455 code is triggered when the Powertrain Control Module (PCM) detects a large leak in the EVAP system, typically greater than 0.080 inches in diameter. This could result from a loose or damaged gas cap, cracked or disconnected hoses, or other issues within the system.

Common Causes of the P0455 Code:

There are several factors that can cause a P0455 code. Some of the most common causes include:

  1. Loose or damaged gas cap
  2. Cracked or disconnected EVAP hoses
  3. Damaged or faulty EVAP canister
  4. Malfunctioning purge valve or vent valve
  5. Issues with the fuel tank or fuel filler neck

Troubleshooting and Repairing the P0455 Code:

To address a P0455 code, follow these troubleshooting steps and tips:

  1. Check the gas cap: The first and simplest step is to inspect the gas cap. Ensure it is properly tightened and in good condition. If there are any signs of damage or wear, replace the gas cap.
  1. Inspect the EVAP hoses: Look for any visible signs of damage, cracks, or disconnections on the EVAP hoses. Replace or reconnect any damaged or disconnected hoses.
  1. Test the purge and vent valves: Use a multimeter to test the electrical connections and functionality of the purge and vent valves. If any issues are found, replace the faulty valve.
  1. Use a smoke machine: To identify less obvious leaks in the EVAP system, using a high-quality smoke machine like the AutoLine Pro automotive smoke machine is highly recommended. This machine will allow you to efficiently locate any leaks within the EVAP system, air intake system, exhaust system, turbo, and more. For more information about smoke testing, here is an article about how to Smoke Test EVAP System to Diagnose a Leak.
  1. Inspect the fuel tank and filler neck: Check the fuel tank and filler neck for any signs of damage or corrosion that could lead to leaks. If any issues are found, repair or replace the faulty components.


The P0455 code can be caused by various factors, but with proper troubleshooting and repair, you can quickly identify and resolve the issue. Using a high-quality diagnostic tool like the AutoLine Pro automotive smoke machine can greatly assist in finding and addressing leaks in your vehicle's EVAP system and other closed systems. Remember, regular maintenance and staying vigilant with potential issues can help prevent more severe problems and keep your vehicle running smoothly for years to come.

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