How do you fix gm code po440?

The GM code P0440 indicates an issue with the evaporative emission control system (EVAP). To fix this, start by inspecting the EVAP system for leaks, such as damaged hoses, loose connections, or a faulty gas cap. You may also need to check the EVAP canister and purge valve for proper operation. If necessary, replace any damaged components and clear the code using an OBD-II scanner before retesting the system.