Intake Air Temperature Sensor

Intake Air Temperature (IAT) sensor is a thermistor which changes its resistance based on temperature of air entering engine. Low air temperatures produces a high resistance of 100,000 ohms at -40°F (-40°C). High air temperatures cause low resistance of 70 ohms at 266°F (130°C). PCM supplies a 5-volt reference signal to IAT sensor through a resistor in the PCM and monitors signal voltage. Voltage will be high when incoming air is cold. Voltage will be low when incoming air is hot. By measuring IAT voltage, PCM calculates incoming air temperature. IAT sensor signal is used to adjust spark timing according to incoming air density. Scan tool displays temperature of air entering engine. Temperature should read close to ambient air temperature when engine is cold and rise as underhood temperature increases. If engine has not been run for several hours (overnight), IAT sensor temperature and engine coolant temperature should read close to each other. A fault in IAT sensor circuit will set DTC P0112 or DTC P0113.