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

The intake air temperature sensor is a thermistor-type sensor mounted in the engine inlet air system. A thermistor resists the flow of electricity similar to a resistor. However, the resistance of a thermistor increases as the temperature drops. For example, at a low air temperature a thermistor produces a high resistance of 100k ohms at -40°C (-40°F), while a high temperature causes low resistance of 241 ohms at 90°C (194°F).

The intake air temperature sensor is a two-wire sensor that receives a reference signal voltage from the PCM to sensor pin B and a sensor reference ground from the PCM to sensor pin A.

The PCM supplies the a five-volt reference signal to the intake air temperature sensor through a current-limiting resistor located inside the PCM. This signal is received by the PCM and indicates the temperature of the air entering the engine. This sensor input is used by the PCM for fuel enrichment, ignition timing, canister purge control, and closed loop fuel control.