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

This sensor, located in the air intake duct between the air filter and intake manifold, is a simple thermistor that receives a 5 volt reference signal from the ECU. The sensor internal resistance, which varies with temperature, determines the sensor voltage signal sent back to the ECU. By comparing the sensor signal voltage to the reference voltage, the ECU can determine manifold air temperature. Air temperature is inversely proportional to density. Therefore when temperature falls, its density increases. The ECU then responds by increasing the amount of fuel as required to maintain the required air/fuel mixture ratio.