Diagnostic Trouble Code P0440

P0440 “Evaporative Emission Control System Malfunction”


What is code P0440?

Code P0440 stands for “Evaporative Emission Control System Malfunction”. This diagnostic trouble code can show up for a number of problems related to a leak in the evaporative emissions (EVAP) system. Therefore, it is important to have a qualified technician diagnose the specific problem that caused the code to be stored in your vehicle’s computer.

Get this checked out soon by a CarAdvise shop, where the work will be guaranteed, and one of our expert techs will review any repair orders.


What does code P0440 mean?

When code P0440 shows up on a diagnostic scan of your vehicle, a technician knows that there is something going wrong with your EVAP system.

Gasoline has a tendency to evaporate, especially when it is warm outside, or when you are filling the gas tank at the pump. This evaporation not only depletes your store of fuel, but also allows harmful pollutants to enter the atmosphere. For this reason, vehicles are fitted with an evaporative emissions control system, also known as the EVAP system. This collection of tubes, sensors, and valves connected to the fuel tank allow evaporating vapors to be collected in a special receptacle, the EVAP canister, where they can be reintroduced into the fuel system to be burned by the engine at a later time.

The ECM (Engine Control Module) that oversees the function of your engine and other systems will run periodic pressure or vacuum tests on the EVAP system to confirm that the system is working properly. If the ECM detects a leak of pressure (or vacuum) that might allow gasoline vapors to enter the atmosphere, or if other components in the EVAP system are failing, it will store a diagnostic code P0440 and turn on the check engine light.

What causes code P0440?

A number of causes can trigger a code P0440. That is why an accurate diagnosis is essential. Causes of this code relate to any component in the EVAP system that could facilitate a leak. For instance:

Most likely

  • A loose or faulty gas cap that does not seal properly ($12-$50)
  • EVAP hose or connector
  • Purge valve (Avg. $144)

Other possibilities

What symptoms are associated with this code?

Common signs associated with a code P0440 include the following:

  • The check engine light is on or flashing
  • Reduced fuel economy
  • Failed emissions test
  • Smell of fuel outside your vehicle

How does a technician diagnose code P0440?

If a diagnostic scan of your vehicle indicates a code P0440, a technician will perform tests to pinpoint the problem. These tests include checking for any related trouble codes. The technician will also use the scan tool to command EVAP components to function, such as opening and closing the purge valve or vent valve, to observe certain characteristics that might indicate which component is leaking. The technician might also employ a device called an evaporative emissions smoke tester to pump smoke into the system and look for leaks.

How serious is this code?

A code P0440 is not likely to cause any immediate drivability issues. It will, however, prevent your vehicle from passing an emissions test. An EVAP system leak can get worse with time and could lead to additional diagnostic trouble codes. In some cases, a fuel vapor leak could even cause engine misfires. Code P0440 is not cause for immediate concern, but it should not be ignored long-term. Look to have your vehicle inspected within a week or so.

Get this checked out soon by a CarAdvise shop, where the work will be guaranteed, and one of our expert techs will review any repair orders.


Related Diagnostic Trouble Codes

P0442 “EVAP System Leak Detected (small leak)”

P0450 “EVAP System Pressure Sensor/Switch A Circuit”

P0456 “EVAP System Leak Detected (large leak)


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