Express 1/2 Ton Van V8-5.7L VIN R (1999)
Intake Air Temperature (IAT) Sensor: Description and Operation
Intake Air Temperature (IAT) Sensor
The Intake Air Temperature (IAT) sensor is a thermistor which changes the value based on the temperature of the air entering the engine. 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.
The scan tool displays the temperature of the air entering the engine, which should read close to the ambient air temperature when the engine is cold. The
temperature should rise as the underhood temperature increases. If the engine has not been run for several hours (overnight), the IAT sensor temperature
and the engine coolant temperature should read close to each other. If the VCM detects a malfunction in the IAT sensor circuit, the following DTCs will
set:
^
DTC P0112 circuit low
^
DTC P0113 circuit high
^
DTC P1111 circuit intermittent high
^
DTC P1112 circuit intermittent low
