E 150 V8-4.6L SOHC VIN W (2004)
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 air flow.
The IAT sensor provides a quicker temperature change response time than the ECT or CHT sensor.
Currently there are two design types of IAT sensors used, a stand alone\non-integrated type (Figure 39) and a integrated (Figure 40) 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. However, one is located before the
supercharger at the air cleaner for standard OBD II/cold weather input, while a second sensor (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.
Currently two types of IAT2 sensors are used. A non-integrated screw in type (Figure 39) and an integrated type, which is part of the Thermal Manifold
Absolute Pressure (TMAP) sensor (Figure 48). The TMAP sensor consists of a IAT thermistor and a manifold absolute pressure (MAP) sensor. The
thermistor portion of the TMAP is used for IAT2 function and operates in the same manner as a non-integrated IAT2. For additional information on the
MAP portion of the TMAP, refer to the Thermal Manifold Absolute Pressure Sensor description and operation found later.
