Mass Airflow (MAF) Sensor
WARNING: This page is about a different car, the 1997 Lexus SC 300. However, it is still accessible from the selected car via links, so may be relevant.
ECM applies a reference voltage to a hot wire in the MAF sensor. As intake air flows across the hot wire, the resistance value changes, causing the reference voltage to change. ECM uses voltage signal to control fuel injection duration and ignition timing.