Intake Air Temperature 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. See Fig 1 or Fig 2 . 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 base 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.