Scion 22204-31020 Meter Sub-Assy, Intake Air Flow

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The Mass Airflow (MAF) sensor is located on the air intake duct and consists of a platinum hot wire, a thermistor, and a control circuit within a plastic housing. The platinum hot wire and thermistor detect even the slightest changes in the temperature of the intake air passing over them. As the throttle opens, more air passes over the hot wire, cooling it. The MAF sensor circuit maintains the hot wire at a constant preset temperature by controlling the current flow through it; as the wire cools, the PCM increases the current to maintain the temperature. The output voltage signal of the MAF sensor varies with this current flow and is measured by the PCM, which converts the signal into a digital waveform, compares it to a map, calculates the necessary fuel injector pulse width, and activates the injectors accordingly. A problem in the MAF sensor circuit will set a diagnostic trouble code. To service the MAF sensor, ensure the ignition key is in the OFF position, disconnect the electrical connector from the MAF sensor, and remove the mounting screws. Twist the MAF sensor out of the air intake duct and remove the O-ring. Installation is the reverse of removal, ensuring a new gasket or O-ring is installed between the MAF sensor and the intake duct.

To remove the MAF sensor, the electrical connector needs to be disconnected first.

The Mass Airflow (MAF) sensor is responsible for measuring the amount of air entering the engine.

For reinstallation, follow the reverse of the removal process. Make sure to use a new O-ring to ensure proper sealing of the MAF sensor in the air filter housing.