Range Rover Sport (LS) V8-4.4L (2009)
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Intake Air Temperature Sensor: Description and Operation
Mass Air Flow/Inlet Air Temperature Sensor (MAF/AT)
The MAF (mass air flow) /IAT (intake air temperature) is located in the clean air duct immediately after the air filter box.
The air mass flow is determined by the cooling effect of inlet air passing over a hot film element contained within the device. The higher the air flow the
greater the cooling effect and the lower the electrical resistance of the hot film element. The ECM (engine control module) then uses this signal from the
MAF (mass air flow) to calculate the air mass flowing into the engine.
The measured air mass flow is used in determining the fuel quantity to be injected in order to maintain the stichometric air/fuel mixture required for
correct operation of the engine and exhaust catalysts. Should the device fail there is a software backup strategy that will be evoked once a fault has been
diagnosed.
The following symptoms may be observed if the sensor fails:
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During driving the engine RPM might dip, before recovering.
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Difficulty in starting or start - stall.
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Poor throttle response / engine performance.
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Lambda control and idle speed control halted.
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Emissions incorrect.
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AFM signal offset
The IAT (intake air temperature) sensor is integrated into the MAF (mass air flow) meter. It is a temperature dependent resistor (thermistor), i.e. the
resistance of the sensor varies with temperature. This thermistor is a NTC (negative temperature coefficient) type element meaning that the sensor
resistance decreases as the sensor temperature increases. The sensor forms part of a voltage divider chain with an additional resistor in the ECM (engine
control module). The voltage from this sensor changes as the sensor resistance changes, thus relating the air temperature to the voltage measured by the
ECM (engine control module).
The ECM (engine control module) stores a 25°C default value for air temperature in the event of a sensor failure.
