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

Intake Air Temperature Sensor Circuit:

Intake Air Temperature Sensor:

PURPOSE
The Intake Air Temperature (IAT) sensor is a thermistor used by the ECM to slightly retard spark timing during high intake manifold air temperatures and delay EGR until the IAT reaches about 5°C (40°).

OPERATION
The ECM supplies a 5.0 volt signal to the IAT sensor through a resistor within the ECM and measures the voltage. By measuring the voltage, the ECM can determine IAT. Low intake manifold air temperature produces high resistance (100,000 ohms at -40°C/-40°F) and high voltage. High intake manifold air temperature produces a low resistance (70 ohms at 130°C/266°F) and low voltage.