Express 1/2 Ton Van V8-305 5.0L VIN M SFI (1998)
Intake Air Temperature (IAT) Sensor: Description and Operation
Intake Air Temperature (IAT) Sensor
PURPOSE
The Intake Air Temperature (IAT) sensor is a thermistor which changes the value based on the temperature of the air entering the engine.
OPERATION
A low temperature produces a high resistance (100,000 ohms at -40°C/-40°F). A high temperature causes a low resistance (70 ohms at 130°C/266°F).
The VCM supplies a 5.0 volt signal to the sensor through a resistor in the VCM 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 VCM calculates the incoming air temperature. The IAT sensor signal is used in
order to adjust the spark timing according to the incoming air density.
DIAGNOSIS
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.
