Lumina V6-204 3.4L DOHC VIN X SFI (1996)
Intake Air Temperature (IAT) Sensor: Description and Operation
Mass Air Flow (MAF) Sensor
DESCRIPTION
The Intake Air Temperature (IAT) sensor is a thermistor which changes value based on the temperature of air entering the engine. 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/286°F). The 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.
The IAT sensor signal is used to adjust spark timing according to incoming air density. The scan tool displays temperature of the air entering the engine,
which should read close to ambient air temperature when 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
should set DTC P0112 or DTC P0113.
