Circuit Operation - UART Data Line

On UART based communication systems, there is a master of the serial data line and remote transceivers. The master controls the message traffic on the serial data line by polling all of the remotes (control modules) and then waiting for the proper response. The control modules on the UART data line are:
^ Electronic Brake (and Traction) Control Module (EBCM/EBTCM)
^ Inflatable Restraint Sensing and Diagnostic Module (SDM)
^ Heater and A/C Programmer or Controller
^ Powertrain Control Module (PCM)
^ Cellular Telephone Module
^ Instrument Cluster