P0440 OBD-II Trouble Code

Technical Description

Evaporative Emission Control System Malfunction

What does that mean?

This indicates that a part of the EVAP control system is no longer fuctioning correctly. The EVAP system consists of many parts, including (but not limited to) the gas cap, fuel lines, carbon canister, purge valve, and other hoses. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Symptoms

You likely won't notice any drivability problems.

Causes

A code P0440 could mean one or more of the following has happened:

• The gas cap is not installed or working properly
• The purge solenoid has failed
• The canister is plugged and not working properly

Possible Solutions

With a P0440 OBD-II trouble code, diagnosis can be tricky at times. Here are some things to try:

• Remove and reinstall the gas cap, clear the code, and drive for a day and see if the codes come back.
• Inspect the EVAP system for cuts/holes in tubes/hoses
• Inspect for damaged or disconnected hoses around the Evap purge solenoid
• Check and/or replace the sensor
• Check and/or replace the purge valve
• Have a professional use a smoke machine to detect leaks

Need more help?

If you still need help regarding the P0440 trouble code, please post your concern in the forums.

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