Bonneville V6-3800 3.8L VIN L SFI (1995)
Intake Air Temperature Sensor: Description and Operation
PURPOSE
The Intake Air Temperature (IAT) sensor signal is used to adjust spark timing according to incoming air density.
OPERATION
The 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 / 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.
The Tech 1 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 Diagnostic Trouble Code (DTC) P0112 or DTC
P0113.
