Rodeo S 2WD L4-2.2L (1999)
Intake Air Temperature Sensor: Description and Operation
Intake Air Temperature (IAT) Sensor
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 about 100,000 ohms at -40 °C (-40 °F). High temperature causes low resistance of about 70 ohms at 130 °C (266 °F).
The PCM supplies a 5-volt signal to the sensor through a resistor internal to the PCM, and then 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 failure in the IAT sensor circuit will set a DTC.
