V90 L6-2.9L VIN 96 B6304S (1998)
Air Flow Meter/Sensor: Description and Operation
The mass air flow (MAF) sensor transmits a signal to the engine control module (ECM) about the intake air mass.
This information is used to calculate:
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injection period
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ignition timing
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if the engine cooling fan (FC) needs to run-on.
The mass air flow sensor consists of a plastic housing containing a connector, electronic circuitry and an aluminum heat sink. The mass airflow sensor
measuring device is a heated film mounted in a pipe which is cooled by the intake air to the engine. The heated film consists of four resistors:
The mass air flow sensor is supplied with battery voltage and has separate power and signal grounds. The signal from the sensor varies from 0 Volts to 5
Volts depending on the mass of air passing. Voltage increases with air mass.
Since working temperature is relatively high (170°C (338°F)), and the flow and temperature sensitive resistors are mounted on the side of the hot film, a
burn-off function is not required.
The engine control module adopts substitute values if the mass air flow sensor signal is missing or faulty.
The mass air flow sensor is located between the air cleaner (ACL) cover and the fresh air intake.
