What is Code po440?

The code should be for a loose gas cap or a bad seal on the gas cap. I got the code one time for not replacing the gas cap after filling up at the gas station.

Also, keep in mind, that code P0440 wont fire until the gas tank is at least 15% empty. So if you fill it up, it will clear the code. When your tank is at 85% full, it will come back on again.

Sometimes the code fires due to a loose gas cap; other times there is a vacuum leak in the EVAP system or a malfunctioning charcoal canister, solenoid , etc in the system.

This is not a critical repair. Your vehicle should drive fine. But you should have it checked for leaks, etc.