Diagram Of Air Flow Through Throttle Body Contacting MAF Sensor Hot and Cold Wire Terminals
The Intake Air Temperature (IAT) sensors (Figure 34) and integrated Mass Air Flow (MAF) type (Figure 37), are thermistor devices in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and 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 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 MAF.
The IAT sensor provides a quicker temperature change response time than the ECT or CHT sensor.
Supercharged 5.4L Lightning vehicles use (2) AT sensors. Both sensors operate as above. However, one is located before the supercharger at the air cleaner for standard OBD II/cold weather input, while a second sensor Second Intake Air Temperature (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 border-line spark and to help determine intercooler efficiency.
