P0440: Evaporative Emission Control System Malfunction

Your evaporative emission control system is an essential combination of fuel vapor hoses, a charcoal fuel vapor storage canister and computer-controlled purge and vent valves. These components capture, store and recycle fuel vapors from the fuel tank and fuel delivery system. If you are unfamiliar with this complex system, you may be wondering, how do I fix trouble code P0440? Learn more about this important system, how to find the cause of the DTC and steps to take to fix the problem.

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What is an Evaporative Emission Control System?

Your vehicle uses this system to collect harmful fuel vapors. Vapors are routed from the fuel tank to the charcoal canister through rubber hoses or plastic tubing. The canister stores the harmful vapors when the engine is not turned on. When the engine is running and certain system parameters are in range, the computer will control the purge valve and vent valve together and purge the stored vapors from the charcoal canister into the engine’s intake system.

When it is operating properly, the EVAP system contains fuel vapors and prevents them from escaping into the environment. A significant leak in this system results in error code P0440. You may or may not notice this leak, but it’s an important issue to promptly fix.

What are the Symptoms of a P0440 Error Code?

Now that you understand the basics of the evaporative emission control system, what does the code P0440 mean? This general code means that there is an issue with one or more parts of the control system. The fuel vapors could be escaping due to a number of failures, including these parts:

  • Gas Cap
  • Purge Valve or Vent Valve
  • Leaking Charcoal Canister
  • Leaking EVAP Hoses
  • Fuel Tank Pressure Sensor

While there could be a significant vapor leak, you won’t notice any difference in the operation of your vehicle. Your Check Engine Light will appear and your OBD-II scanner will read an error code P0440. Leaking fuel vapors can be dangerous, so you should still make it a priority to inspect your evaporative emission control system even if you don’t notice any performance issues.

What Causes P0440?

Because of the many parts that could cause a fuel vapor leak, you’ll need to inspect each part to find the solution. However, some solutions are very simple to perform. Try the first few solutions, clear the error code, and drive your vehicle for at least a day. If the code returns, you’ll need to perform more complex repairs.

How to Fix P0440 Codes

The easiest solution is to check for a loose gas cap. A loose gas cap can cause fuel vapors to escape and signal this DTC. Or, the gas cap could be bad and cause the same issue. If the gas cap is not loose, replacing it is the easiest way to check out the problem. However, if the gas cap isn’t the solution, your evaporative emission control system will continue to malfunction.

Other parts to inspect / check are the rubber or plastic EVAP lines. Also, the purge and vent valves, charcoal filter, and charcoal canister. A failed or improperly working purge or vent valve could be the solution to your error code P0440.

The most complex solution is a small cut or hole in the evaporative emission control system hoses / tubing. A tiny cut could cause a large enough vapor leak to create the problem code, so you need to carefully inspect the entire length of fuel lines and hoses. A more efficient solution is to use a professional smoke machine for detecting leaks in the EVAP lines.

Once you find the OBD-II scanner error code P0440 problem, you’ll be able to restore your evaporative emission control system and prevent excessive fuel vapor leaks from harming your health or affecting the environment. You can get the parts you need at your local AutoZone Store. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

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