The microprocessor controlled modules in the vehicle communicate
with each other through the serial data line. The vehicle uses the three following
serial data lines:
| • | The class 2 serial data line |
| • | The E&C serial data line |
| • | The simple bus interface (SBI) serial data line |
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 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). The master then waits for the proper response. The
control modules on the E&C data line can include:
| • | The heater and A/C programmer |
| • | The compact disc (CD) player |
| • | The Remote Function Actuator (RFA) Module |
Class 2 Serial Data Line
Class 2 data transmits at a higher speed and the 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 can include:
| • | The body control module (SBM) |
| • | The driver door module (DDM) |
| • | The electronic brake/traction control module (EBTCM) |
| • | The heater and A/C programmer |
| • | The inflatable restraint sensing diagnostic module (SDM) |
| • | The memory seat module (MSM) |
| • | The theft deterrent module |
| • | The powertrain control module (PCM) |
| • | The remote function actuator (RFA) module |
Simple Bus Interface (SBI) Serial Data Line
The simple bus interface is used for serial data communications between
the door modules. The control modules on the simple bus interface serial data
line are:
| • | Driver Door Module (DDM) |
| • | Passenger Door Module (PDM) |
