The MAF sensor (Mass Air Flow Sensor) measures the volume and density of air entering the engine. This sensor is usually located in the intake near the air cleaner. Although this sensor only measures a portion of the air entering the engine, this value is used to calculate the total volume and density of the air.
The Powertrain Control Module (PCM) ensures that the fuel delivery at different driving points is right by reading the MAF Sensor and other data from it. The PCM makes this process in order to achieve higher engine power and fuel efficiency.
The P00BD OBDII fault code setting occurs when the PCM detects the Mass Air Flow Sensor A circuit has a condition in which the air flow is excessively high.