How do you fix OBD II Code PO171?

OBD II Code P0171 indicates a lean fuel mixture, meaning the engine is getting too much air or not enough fuel. To fix this code, first check for vacuum leaks in hoses and gaskets, as these can allow excess air into the intake. Additionally, inspect the mass air flow (MAF) sensor for dirt or malfunction and clean or replace it if necessary. Lastly, ensure that the fuel system, including the fuel pump and injectors, is functioning properly and providing adequate fuel pressure.