C 1500 Truck 2WD V8-5.3L VIN T (1999)
Intake Air Temperature (IAT) Sensor: Description and Operation
The Intake Air Temperature (IAT) sensor is incorporated into the MAF sensor component body. 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 -38°C1-39°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. The PCM calculates the incoming air temperature by
measuring the IAT voltage. 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. The following DTCs set if the PCM detects a malfunction in the IAT sensor circuit:
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DTC P0112 IAT Sensor Circuit Low Voltage.
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DTC P0113 IAT Sensor Circuit High Voltage.
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DTC P1111 IAT Sensor CKT Intermittent High Voltage.
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DTC P1112 IAT Sensor CKT Intermittent Low Voltage.
