Theory Of Operation

WARNING: This page is about a different car, the 2017 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. The PCM communicates with external control modules via a serial multiplexed data link bus using Controller Area Network (CAN) protocol. An implausible signal failure condition refers to a signal received across the data link in which the integrity of the data being transmitted or received has been compromised. This is also referred to as a Lost Ambient Temperature Message. The implausible diagnostic on these signals monitors the messages being received for Signal Not Available (SNA) status. The PCM will illuminate the MIL lamp after the diagnostic runs and fails in two consecutive drive cycles.