What causes OBDII code P0440?

Answer 1

The 0400 - 04## are all emissions related, can be caused by something as trivial as an improperly tightened gas cap or as complex as the EVAPORATIVE EMISSIONS CONTROL SYSTEM, which has a series of hoses, purge valve and charcoal vapor canister filter controlled by the computer. Older cars normally develop leaks in the hoses that can be determined using specialized leak detection testing, normally not for diy level of repair. Most of the 0400 series codes will not affect drive-ability but should be treated ASAP