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

Engine Coolant Temperature (ECT) Sensor:

PURPOSE
The Intake Air Temperature (IAT) sensor is a thermistor (a resistor which changes value based on temperature). It is mounted in the air intake duct. The intake air temperature along with manifold pressure and engine RPM are utilized by the PCM to determine base fuel mixture delivered to the fuel injection system.

OPERATION
The Powertrain Control Module (PCM) supplies a 5 volt signal to the sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the intake air is cold and low when the intake manifold air is hot. By measuring the voltage, the PCM knows the intake air temperature. A failure in the IAT sensor circuit should set either a DTC 23 or DTC 25.