This vehicle is equipped with a computer system capable
of performing multiple engine and body control functions. Vehicle components
(windows, locks, mirrors, etc.) are controlled directly by their system
module. Each system communicates with other systems on an ``interconnecting
bus'' or serial data circuit. The following systems are all part of
the vehicle's computer system providing two-way communication between
various engine and body control systems.
| • | Powertrain Control Module (PCM) |
| • | Traction Control System (TCS) |
| • | Real Time Damping (RTD) * |
| • | Body Control Module (BCM) |
| • | Instrument Panel Cluster (IPC) |
| • | Sensing and Diagnostic Module (SDM) |
| • | Heater, Ventilation and Air Conditioning (HVAC) (with CJ2) * |
| • | Left Door Control Module (LDCM) |
| • | Right Door Control Module (RDCM) |
| • | Seat Control Module (SCM) * |
| • | Remote Function Actuation (RFA) * |
* Optional
Communications between each system is accomplished by sending a digitally
coded message, consisting of specific information a system module must follow.
Some electrical components are directly connected and controlled by
their system module. Others systems accomplish this by sharing data
information with other systems on the serial data circuit to execute
various vehicle functions. All system data information (sensors, switches,
etc.) can be monitored by any system module that completes the vehicle's
computer system. All systems 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 this information between each system connected to the
serial data circuit. Each system is assigned a specific recognition
code (source ID). This code is used to identify which module is communicating
on the serial data circuit. So when a message is sent out on the serial
data circuit , the recognition code (source ID) will identify which particular
module sent the message. These messages contain specific information
(or commands) a system 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
actually sent the message and for State of Health (SOH) monitoring.
SOH monitoring determines if a system is unable to communicate properly.
By communicating data information with other systems on the same serial
data circuit, either input information or specific program information
within the module's memory, can provide more accurate and reliable
computer system control functions. Description and diagnosis of each
system will be covered in the respective service manual section.
