Theory Of Operation
WARNING: This page is about a different car, the 2019 RAM 3500 HD and 2019 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of this diagnostic is to detect Input Speed Sensor circuit failures. Failures are detected by an Application-Specific Integrated Circuit (ASIC) which communicates with the main microprocessor via a Serial Peripheral Interface (SPI) bus. The ASIC is integrated in the Transmission Control Module (TCM).