Check Engine Code P0440

Do you know what is wrong with your car when it flashes a P0440 code? Learn all about this OBD code and how to fix it from an experienced mechanic.

This code appears when the computer detects your EVAP system is not working correctly. What is an EVAP system? Well all it really is is a way for the fumes that are generated from your fuel sloshing around and expanding on hot days to be stored until they can be sucked into the engine and burnt.

In order to do this, car makers put a charcoal canister (this part just stores all of these fumes) in the engine compartment and install hoses between this canister and the fuel tank.

When there are too many fumes to fit into the gas tank they all travel through these hoses to the charcoal canister and they are kept there until the computer determines that they can be used in the engine and it opens a valve to let them be sucked into the engine. One of these hoses or the valve that lets the fumes go into the engine malfunctions then there would possibly be gas fumes going into the air.

This is not good for anyone so when the computer sees this happening it will trigger this OBD code.

Possible Causes of P0440 Code

  • A Leak in the System
  • Faulty Purge Solenoid (This is the valve that lets the fumes into the engine)
  • Faulty or loose fuel cap
  • Faulty or Loose NVLD (This is the sensor that senses whether the system is working or not)

Less Common Causes

  • The Computer
  • Leaky Fuel Tank
  • Bad Charcoal Canister

To troubleshoot, repair and maintain your vehicle, you'll need diagnostic and repair information that is specific to your car or truck. For this I personally use and recommend ALLDATAdiy. With full manuals for over 30,000 vehicles online, you will find an exact match for your vehicle's year, make and model.

Besides being cheaper than a factory manual, they also offer step by step repair instructions and detailed diagrams beyond what is found in most printed manuals. Click here for a sample of their diagnostic and repair information.

How to Fix Engine Code P0440

The first thing to try is re-installing your fuel cap as this can cause this code and is an easy fix. If you suspect the cap might be bad, then you might want to just replace it. You can also check for any loose or damaged hoses under your hood. They can cause this type of code.

If that does not fix it then I recommend taking your car to a good repair shop. They will have what is called a "smoke machine". This machine puts smoke into the whole system and then they can see exactly where it is leaking. There is no other good way of checking for leaks in this system. It will save anyone lots of time and money to just take your car somewhere that has the capability to perform this test.

If you still have any unresolved vehicle problems or questions, you can ask an auto mechanic online. For expert answers specific to your vehicle's make and model, I recommend JustAnswer Car. They have a large pool of certified mechanics to answer your questions for a small fee and you can also browse their answers to other users for free.

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