Mass Airflow (MAF) Sensor
The MAF sensor provides a signal to the PCM proportional to the intake air mass. The MAF sensor uses a hot wire sensing element to measure the amount of air entering the engine. The hot wire is maintained at a constant temperature above ambient. Air passing over the hot wire cools the wire. The current required to maintain the temperature of the hot wire is proportional to the airflow.
The MAF sensor is a digital sensor that provides an output signal of varying frequency. The signals time period is proportional to the flow rate crossing the sensor. The greater the airflow the shorter the time period. The time period varies from 1480 microseconds at a low flow or idle condition, to 106 microseconds at a high flow rate condition.
The IAT sensor is integrated with the mass airflow (MAF) sensor. The MAF/IAT sensor is located in the intake air tube between the air filter housing and the turbocharger intake. On some vehicles the turbocharger inlet pressure (TCIP) sensor and a relative humidity sensor is integrated with the MAF/IAT sensor.
Typical MAF/IAT/TCIP/RHS Sensor