Theory Of Operation

WARNING: This page is about a different car, the 2015 RAM 3500 HD and 2015 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The Ambient Air Temperature (AAT) Sensor is located in the driver's door mirror. The Driver's Door Module (DDM) receives the data from the AAT sensor and sends it to the Body Control Module (BCM). The BCM then passes the data on to the Powertrain Control Module (PCM). There are two rationality tests. The first test is: Ignition on/engine running. The second test is: After an eight hour cold soak, at key on the readings for the AAT, Charge Air Cooler (CAC) temperature (D2, DJ), Intake Manifold Temperature (DD, DP), and the Engine Coolant Temperature (ECT) Sensors are all compared. If the temperatures differ by more than a calibrated amount, then the appropriate sensor fault code would be recorded. The PCM rationality check looks at the temperature reading from the sensor over time and ensures that it changes with the engine running. If the sensor reading does not change over a calibrated time limit, the fault will be recorded. The PCM will illuminate the MIL lamp after the diagnostic runs and fails in two consecutive drive cycles.