Tundra Access Cab SR5 4WD V8-4.7L (2UZ-FE) (2001)
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Mass Air Flow Meter: Description and Operation
Mass Air Flow Meter
The mass air flow meter uses a platinum hot wire. The hot wire air flow meter consists of a platinum hot wire, thermistor and a control circuit installed in
a plastic housing. The hot wire air flow meter works in principle that the hot wire and thermistor located in the intake air bypass of the housing detect any
changes in the intake air temperature.
The hot wire is maintained at the set temperature by controlling the current flow through the hot wire. This current flow is then measured as an output
voltage of the mass air flow meter.
The circuit is constructed so that the platinum hot wire and thermistor provide a bridge circuit, with the power transistor, and controlled so that the
potential of A and B remains equal in order to maintain the set temperature.
