Theory Of Operation

The Intake Air Temperature (IAT) Sensor 3 is located at the Turbocharger before the Charge Air Cooler. It is sometimes referred to as the 'Charge Air Cooler Upstream Temperature' Sensor. The described rationality check will detect the IAC Sensor 3 has an output which is inappropriately high (i.e. in range high) or inappropriately low (i.e. in range low). The temperature sensed by the IAC Sensor 3 is compared to the Ambient Air Temperature Sensor after a sufficient amount of engine-off time. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.