240 L4-2320cc 2.3L SOHC VIN 83 B230FD (1993)
Air Flow Meter/Sensor: Description and Operation
Mass Air Flow Sensor (LH-3.1)
Air Mass Meter
Hot-Film Element (Part Of Air Mass Meter)
PURPOSE
The mass air flow sensor provides the injection ECU with continuous information regarding intake "air mass." The injection ECU also forwards
engine load information to the ignition ECU.
LOCATION
Mounted on the air cleaner housing, top cover.
CONSTRUCTION
The mass air flow sensor is a hot-film sensor type with 4 resistances. The unit consists of a plastic housing containing a connector, electronic
circuitry, and an aluminum heat sink.
Each film resistance performs a different function:
Rt, Temperature sensitive NTC-type resistance signal. Supplies information regarding intake air temperature.
R1, Calibration resistance.
Rs, Flow sensitive PTC-type resistance signal. Also supplies information regarding the cooling effect of intake air.
Rh, Heating resistance. Maintains the temperature of Rs at 340°F (170°C) above intake air temperature.
OPERATION
The mass air flow sensor uses an electronic unit to measure the current required to maintain the temperature of Rs at 340°F (170°C) above intake
air temperature.
The flow required to maintain the temperature constant is proportional to the mass of air flow. The electronic unit measures the quantity of current
required to maintain the Rh resistance at a constant temperature above the Rs resistance.
