Grand Marquis V8-4.6L Flex Fuel (2010)
Intake Air Temperature Sensor: Description and Operation
ENGINE CONTROL COMPONENTS
Intake Air Temperature (IAT) Sensor
The IAT sensor is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the
temperature increases, and the resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor
terminals and provides electrical signals to the PCM corresponding to temperature.
Thermistor-type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of
the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in a series with the sensor resistor determines
the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.
The IAT sensor provides air temperature information to the PCM. The PCM uses the air temperature information as a correction factor in the
calculation of fuel, spark, and air flow.
The IAT sensor provides a quicker temperature change response time than the ECT or CHT sensor.
Currently there are 2 types of IAT sensors used, a stand-alone/non-integrated type and an integrated type. Both types function the same, however the
integrated type is incorporated into the mass air flow (MAF) sensor instead of being a stand-alone sensor.
Supercharged vehicles use 2 IAT sensors. Both sensors are thermistor type devices and operate as described above. One is located before the
supercharger at the air cleaner for standard OBD/cold weather input, while a second sensor, intake air temperature 2 (IAT2), is located after the
supercharger in the intake manifold. The IAT2 sensor located after the supercharger provides air temperature information to the PCM to control spark
and to help determine charge air cooler (CAC) efficiency.
The IAT2 sensor for speed density control systems is centrally located on the intake manifold. The IAT2 sensor measures the intake manifold
temperature. The powertrain control module (PCM) uses the information from the IAT2 sensor to determine the speed density air charge and provide
input used for various spark control functions. The IAT2 sensor for a speed density system is integral with the manifold absolute pressure (MAP)
sensor.
Typical Stand-Alone/Non-Integrated IAT Snesors
