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

Intake Air Temperature Sensor:

The Intake Air Temperature Sensor uses a thermistor to control the signal voltage to the ECM. When the air is cold, the sensor resistance is high. When the air is warm the sensor resistance is low. The ECM supplies a 5 volt signal to the sensor through a resistor in the ECM 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 ECM knows the equivalent intake air temperature. With this information, the ECM can delay EGR valve operation until intake air temperature reaches about 40~F (4.4~C). The ECM can also use this information to slightly retard the ignition timing during high ambient air temperature.