Cutlass Ciera L4-2.2L VIN 4 (1995)
Intake Air Temperature (IAT) Sensor: Description and Operation
PURPOSE
The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. The IAT sensor
signal is used in starting and running fuel control calculations.
OPERATION
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 Powertrain Control Module (PCM) supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the voltage. The
voltage will be high when the incoming air is cold, and low when the air is hot. By measuring the voltage, the PCM calculates the incoming air
temperature.
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 should set Diagnostic Trouble Code (DTC) 23 or DTC 25.
