The DTC code P0447 OBD2 is set at the time the PCM (Powertrain Control Module) detects a short in the circuit that controls the vent valve or the solenoid for the EVAP (Evaporative Emission Control System).
When fuel settles in the tank, fuel vapor escapes while the vehicle is being driven. At the same time, a vent is opened allowing the vapors to circulate to the engine intake manifold to a carbon canister or the atmosphere, depending on the vehicle. It is separate from the EVAP.