Theory Of Operation

The Humidity Sensor is internal to the Mass Airflow Sensor (MAF). The internal Humidity Sensor reading gives the PCM an indication of the current presence of water in the air during driving conditions. The PCM uses this information to help calculate fuel delivery. The PCM receives a Humidity reading from the MAF Sensor with the ignition on, before the engine is cranking or running. This Humidity reading from the MAF Sensor is used by the PCM, along with other inputs to calculate fuel delivery, and timing needs.