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

The Intake Air Temperature (IAT) sensor is a thermistor (a resistor which changes value based on temperature) mounted in the air intake snorkel.

Low temperature produces a high resistance (100,000 ohms at -40°C (-40°F) while high temperature causes low resistance 70 ohms at 130°C (266°F).

The control module supplies a 5 volt signal to the sensor through a resistor in the control module and measures the voltage. The voltage will be high when the manifold air is cold, and low when the air is hot. By measuring the voltage, the control module knows the Intake Air Temperature (IAT).

The IAT sensor signal is used by the control module to delay Exhaust Gas Recirculation (EGR) until the Intake Air Temperature (IAT) reaches about 5°C (40°F). The control module uses the signal to slightly retard the timing during high ambient air temperatures.