Trooper LS V6-3.5L (1998)
Intake Air Temperature Sensor: Description and Operation
General Description
The intake air temperature (IAT) sensor is a thermistor which changes its resistance based on the temperature of air entering the engine. Low
temperature produces a high resistance of 100,000 ohms at -40°C (-40°F). High temperature causes low resistance of 70 ohms at 130°C (266°F). The
PCM supplies a 5-volt signal to the sensor through a resistor in the PCM and monitors the signal voltage. The voltage will be high when the incoming
air is cold. The voltage will be low when the incoming air is hot. By measuring the voltage, the PCM calculates the incoming air temperature. The IAT
sensor signal is used to adjust spark timing according to the incoming air density.
The scan tool displays the temperature of the air entering the engine. The temperature should read close to the ambient air temperature when the
engine is cold and rise as underhood temperature increases. If the engine has not been run for several hours (overnight), the IAT sensor temperature
and engine coolant temperature should read close to each other. A fault in the IAT sensor circuit will set DTC P0112 or DTC P0113.
