Circuit Operation - Data Link Communications

The serial data line is the means by which the microprocessor controlled modules in the vehicle communicate with each other. There are several serial data lines on this vehicle, including Class 2, E & C and Simple Bus Interface (SBI)

E & C Serial Data Line
The E&C serial data line is a UART based communication system. UART serial data lines have a master of the serial data line and remote transceivers. The master of this data line is the HVAC Programmer. The master controls the message traffic on the serial data line by polling all of the remotes (control modules) and then waits for the proper response. The control modules on the UART data line are:
^ HVAC Programmer
^ Radio
^ Compact Disc (CD) Changer

Class 2 Serial Data Line
Class 2 data is transmitted at a higher speed and messages are configured differently than UART data. While UART uses a master to control serial data line traffic, Class 2 uses the peer to peer method along with message arbitration to manage data line traffic. The control modules on the Class 2 data line are:
^ Body Control Module (SBM)
^ Cellular Telephone Module (if equipped)
^ Driver Door Module (DDM)
^ Electronic Brake/Traction Control Module (EBTCM)
^ Heater and A/C Programmer
^ Instrument Cluster
^ Inflatable Restraint Sensing Diagnostic Module (SDM)
^ Memory Seat Module (MSM) (if equipped)
^ Pass-Key(R) III Control Module
^ Powertrain Control Module (PCM)
^ Remote Function Actuator (RFA) Module

Simple Bus Interface (SBI) Serial Data Line
The Simple Bus Interface is used for serial data communication of between the three door modules, the Driver Door Module (DDM), the Passenger Door Module (PDM) and the Rear Door Module (RDM). Electrical input and output devices within the doors are wired to the corresponding door modules; the power door locks, power windows, power mirrors, jamb switches, and cylinder switches are all controlled this way.