Air flow sensor is used to determine the amount of air drawn into the engine cylinders. The output signal can be a linearly changing voltage or a changing frequency, depending on type and manufacturer. Types:
– Volume air flow sensor
– Hot element mass air flow sensor
– Hot wire mass air flow sensor
– Hot film mass air flow sensor
– Karman vortex air flow sensor

Typical location of the mass air flow sensor.

Connection of the USB Autoscope IV to the sensor signal wire.

Setting the USB Autoscope IV to the mass air flow sensor testing mode.

Output voltage waveform from BOSCH HFM5 mass air flow sensor in good condition on an Alfa Romeo 156 2.0i 2001, recorded during snap throttle.

Output voltage waveform from a malfunctioning BOSCH HFM5 mass air flow sensor on an Alfa Romeo 156 2.0i 2001, recorded during snap throttle.

Output voltage waveform from a properly functioning volume air flow sensor based on the potentiometer (BMW 318 1.8i 1996). The waveform was recorded during snap throttle.

Output voltage waveform from a properly functioning mass air flow sensor. (Toyota Avensis 1.8i 2007).

Output voltage waveform from a properly functioning air flow sensor BOSCH HFM5 (Alfa 156 2.0i 2001). Snap throttle.

Moment of snap throttle.

Output voltage waveform from a properly functioning air flow sensor BOSCH HFM5. Moment of turning the ignition on.

Output voltage waveform from a properly functioning mass air flow sensor with a frequency output (Opel Vectra C 2.2i 2006). KOEO (Key On Engine Off).

The engine is at idle.

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