Mass Airflow Meter

Airflow meter measures intake airflow rate by measuring a part of entire airflow. Measurements are made so ECU receives electrical output signals varied by amount of heat emitting from a hot film placed in the stream of intake air.

When intake air flows into intake manifold through a route around the hot film, heat generated from hot film is taken away by air. The amount of heat reduction depends on airflow. Temperature of hot film is automatically controlled at a predetermined heat.

Therefore, it is necessary to supply the hot film with more electric current in order to maintain temperature of hot film. ECU detects airflow by means of this current change.

If airflow meter output current is outside of normal operational range, ECU senses an airflow meter malfunction. ECU will then take driving condition information from throttle position sensor. During this period, ECU limits engine speed to less than 2000 RPM. This alerts driver vehicle is operating under fail-safe conditions and needs attention.