Intake Air Temperature (IAT) Sensor

IAT sensor is a thermistor (temperature sensitive resistor). Air temperature of -40°F (-40°C) produces a high resistance (100,000 ohms), while air temperature of 266°F (130°C) produces a low resistance (70 ohms).

PCM supplies a 5-volt reference signal through an internal resistor to IAT sensor and measures return voltage. Voltage is high when air temperature is low, and low when air temperature is hot. Engine air temperature affects fuel delivery and injector timing.