Envoy 2WD V6-4.3L VIN W (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 value based on the temperature of air entering the engine.
OPERATION
Low temperature produces a high resistance 100,000 ohms at -40° (-40°F). A high temperature causes low resistance 70 ohms at 130°C (266°F). The
PCM supplies a 5.0 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. The
temperature should 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. 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.
