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if you have a 3vz, you have an AFM (Air Flow Meter, commonly called a flap meter)... if you have a 1mz, you have a MAF (Mass Air Flow sensor, commonly called hot-wire meter). If you have a 5s-fe, you have no air flow sensor, just a MAP(Manifold Air Pressure) sensor, and air intake temp sensor.
AFM reads the amount of air passing through it by how far the flap opens. It also has a built in temp sensor.
MAF reads the amount of air passing through it like this... A constant voltage is applied to the heated wire. This wire is positioned in the air stream and is heated by the electrical current that the voltage produces. As air flows across it, it cools down. The heated wire is a positive temperature coefficient (ptc) resistor. This means that it's resistance drops when it's temperature drops. The drop in resistance allows more current to flow through it in order to maintain the programmed temperature. This current is changed to a voltage which is sent to the computer and interpreted as air flow on a 0-5V scale. Adjustments for air temperature and humidity are taken into consideration since they also affect the temperature of the heated wire or film.
MAP sensor detects the pressure in the manifold, and sends that to the ECU as a 0-5V signal
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Linear Mode
