Intake Air Temperature Sensor Description
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The Intake Air Temperature (IAT) sensor is a thermistor, a resistor which changes value based on the temperature of the air entering the engine. Low temperature produces a high resistance (4,500 Ω at -40 °C [- 40 °F]), while high temperature causes a low resistance (70 Ω at 130 °C [266 °F]).
The Engine Control Module (ECM) provides 5 V to the IAT sensor through a resistor in the ECM and measures the change in voltage to determine the IAT. The voltage will be high when the manifold air is cold and low when the air is hot. The ECM knows the intake IAT by measuring the voltage.
The IAT sensor is also used to control spark timing when the manifold air is cold.
A failure in the IAT sensor circuit sets a diagnostic trouble code P0112 or P0113.