Air Temperature Sensor ( Ambient / Intake ): Description and Operation

PURPOSE
The Intake Air Temperature (IAT) sensor measures the temperature of the intake air flow. The Powertrain Control Module (PCM) uses this information to adjust the fuel injection base pulse width, and ignition timing.

CONSTRUCTION
The IAT is a two lead thermistor type sensor with a negative temperature coefficient, located in the intake air flow path in the air cleaner housing.

OPERATION
The PCM applies a 5.0 volt reference voltage to the IAT signal lead while the signal return lead is connected to a common sensor ground. As the temperature of the incoming air increases the resistance of the IAT decreases and the voltage drop across the IAT decreases.

A decrease in air temperature will increase the resistance of the IAT and raise the voltage drop across the sensor.

The normal operating range of the IAT is 3.50 volts (50°F) to 1.02 volts (158°F).

Note: Due to its negative temperature coefficient, minor increases in resistance across the IAT circuit harness and ground connections can result in temperature values that are much lower than actual.