Cavalier L4-2.2L VIN 4 (1998)
Intake Air Temperature (IAT) Sensor: Description and Operation
The Intake Air Temperature (IAT) sensor is a thermistor (a resistor which changes value based on the temperature of air entering the engine), similar to
the ECT sensor. Low temperature produces a high resistance (100,000 ohms at -40°C/-40°F) while high temperature causes low resistance (70 ohms at
130°C/266°F). The PCM supplies a 5 volt signal to the IAT sensor through a resistor in the PCM and monitors the terminal voltage. The voltage will be
high when the intake air is cold, and low when the intake air is hot. By measuring the voltage, the PCM knows the intake air temperature. This input is
used in starting and running fuel control calculations. A fault in the IAT sensor circuit should set either a DTC P0112 or DTC P0113.
