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

Intake Air Temperature Sensor:

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

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

Descriptive Schematic:

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.

RELATED DIAGNOSTIC TROUBLE CODES

DTC 112 - The IAT sensor output is less than the self-test minimum, 0.2 volts.

DTC 113 - The IAT sensor output is greater than the self-test maximum, 4.6 volts.

DTC 114 - The IAT sensor output is out of self-test range, 0.3-3.7 volts.