Mass Airflow Meter (G20)

Mass airflow meter uses a hot wire type sensing element. Hot wire is heated to a precalibrated temperature by ECU. Incoming air passing through airflow meter causes hot wire to cool, resulting in the need for ECU to apply additional current to maintain precalibrated hot wire temperature. ECU measures airflow by monitoring change in required current supplied to hot wire.

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.

Since hot wire is exposed to atmospheric contamination, ECU is programmed to clean hot-wire each time ignition switch is cycled off. This is accomplished by heating hot wire to 1832°F (1000°C) for one second after ignition has been turned off for 5 seconds.