What is a Mass Air Flow sensor (MAF)?
The mass air flow sensor is located directly in the intake air stream, between the air cleaner and throttle body where it can measure incoming air. The mass air flow sensor converts the amount of air drawn into the engine into a voltage signal. The ECM (Electronic Control Module) needs to know intake air volume to calculate engine load. This is necessary to determine how much fuel to inject, when to ignite the cylinder, and when to shift the transmission. The 4Runner uses a “Hot Wire” type, mass air flow sensor. The primary components of the MAF sensor are a thermistor (a type of resistor whose resistance varies with temperature), a platinum hot wire, and an electronic control circuit. The thermistor measures the temperature of the incoming air. The hot wire is maintained at a constant temperature in relation to the thermistor by the electronic control circuit. An increase in air flow will cause the hot wire to lose heat faster and the electronic control circuitry will compensate by se
