This vehicle is equipped with a computer system capable of performing
multiple engine and body control functions. Vehicle components such as windows,
locks, mirrors, etc. are controlled directly by their system control module.
Each system control module communicates with other system control modules
on a serial data circuit. The vehicle system control modules are all attached
to the serial data circuit that provides the data link communications. This
data link, or serial data circuit, provides 2-way communication between various
engine and body control system control modules.
The control modules connected to the class 2 serial data circuit
are listed below:
| • | Powertrain Control Module (PCM) |
| • | Electronic Brake Control Module (EBCM) |
| • | Electronic Suspension Control (ESC) Module * |
| • | Body Control Module (BCM) |
| • | Instrument Panel Cluster (IPC) |
| • | Sensing and Diagnostic Module (SDM) |
| • | HVAC Control Assembly (HVAC) (with CJ2) * |
| • | Driver Door Module (DDM) |
| • | Passenger Door Module (PDM) |
| • | Seat Control Module (SCM) * |
| • | Remote Control Door Lock Receiver (RCDLR) * |
* If equipped.
Some electrical system components are directly connected to and controlled
by their system control module. Others systems accomplish the control functions
by sharing data information with other system control modules on the serial
data circuit to execute various vehicle functions. All system data information
from sensors, switches, etc. can be monitored by any system module that is
connected to the serial data circuit. Communications between each system control
module is accomplished by sending a digitally coded message consisting of
specific information. Communicating data information with other system control
modules on the same serial data circuit, either input information or specific
program information, provides more accurate and reliable computer system control
functions.
All system control modules on the same serial data circuit use a communication
process similar to a telephone system, where enormous amounts of information
can be exchanged on a single data wire. The serial data circuit is used to
communicate information between each system control module. Each system control
module is assigned a specific recognition code, called a source ID. This code
is used to identify which module is communicating on the serial data circuit.
When a message is sent out on the serial data circuit , the recognition code
will identify which particular module sent the message. These messages contain
specific information, or commands, a system control module requires to function
properly.
When a system receives a message it also "learns" the source
ID of the system that sent it. This source ID is used to determine which system
control module actually sent the message for State of Health (SOH) monitoring.
SOH monitoring determines if a system control module is unable to communicate
properly. Description and diagnosis of each system and control module is covered
in the respective service manual section.
