Intake Air Temperature Sensor
Intake Air Temperature (IAT) sensor is mounted in near throttle body. See Fig 1 or Fig 2 . The IAT sensor is a 2-wire Negative Thermal Coefficient (NTC) sensor. As intake air temperature increases, voltage decreases. As intake air temperature decreases, voltage increases. The IAT sensor provides an input voltage to the PCM indicating intake air density based on temperature. The IAT sensor input is used by the PCM to calculate fuel injector pulse width and ignition timing spark advance. The resistance values are the same as the Engine Coolant Temperature (ECT) sensor.
The 2-wire Intake Manifold Air Temperature (IAT) sensor is installed in the intake manifold with the sensor element extending into the air stream. The IAT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as intake manifold temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases. The IAT sensor provides an input voltage to the Powertrain Control Module (PCM) indicating the density of the air entering the intake manifold based upon intake manifold temperature. At key-on, a 5-volt power circuit is supplied to the sensor from the PCM. The sensor is grounded at the PCM through a low-noise, sensor-return circuit. The PCM uses this input to calculate injector pulse width and adjustment of spark timing (to help prevent spark knock, with high intake manifold, air-charge temperatures). The resistance values of the IAT sensor is the same as for the Engine Coolant Temperature (ECT) sensor.