Dynasty L4-153 2.5L SOHC VIN K TBI (1992)
Body Controller: Description and Operation
Description and Functional Operation
General Description
The body system consists of a combination of modules that communicate over the CCD bus. Through the CCD bus, information about the operation of
the vehicle components and circuits is relayed quickly to the appropriate module(s). Each module receives the same information about a component or
circuit as every other module does. This significantly reduces the complexity of the wiring in the vehicle and the size of wiring harnesses.
The Chrysler Collision Detection multiplex system (CCD Bus) consists of a twisted pair of wires which run from module to module transmitting and
receiving coded information. The code is designed to identify the message it represents as well as the importance of the message. When there are
multiple messages trying to access the CCD bus at one time, the code is used to determine which message has higher priority, and that one is allowed
to access the bus first.
The two wires (D1) and (D2) of the twisted pair that make up the CCD multiplex system are called "bus +" (bus plus) and "bus -" (bus minus). Both
wires have a measurable voltage level of roughly 2.5 volts. A voltage divider network maintains the 2.5 volts on each bus wire and provides a means
of transportation for the coded messages. This network consists of some modules with bias and some with termination. Bias is the part of the voltage
divider network which places both bus + and bus - at 2.5 volts. Termination is the part of the circuitry required to complete the voltage divider
network as well as provide some electromagnetic protection for the bus. Terminations in all CCD applications have approximately 120 ohms of
resistance.
NOTE: Communication over the CCD bus is essential to the proper operation of the vehicle's on-board diagnostic systems and the DRBII. Problems
with the operation of the bus or DRBII must be corrected before proceeding with diagnostic testing. If there is a problem, refer to the Information Bus
for diagnostic and repair procedures.
Functional Operation
Body Controller
There are three body controllers available in 1992: the "base" controller and two "premium" body controllers. Which "premium" controller the vehicle
has depends on the presence of an electronic instrument cluster.
The body controller provides power and ground for a variety of systems. It uses a voltage drop to monitor these systems.
The body controller is the only module that has the capability of providing both bias and termination on the CCD bus system.
The body controller receives information from the engine node about brake fluid level, engine coolant level, and engine oil level.
The body controller is used to store odometer information displayed in the electronic instrument cluster (see the "Electronic Instrument Cluster"
description later in this section).
NOTE: When replacement of the body controller is required, contact your service center to obtain an exchange body controller.
Electronic Instrument Cluster
The electronic instrument cluster includes a digital speedometer, odometer, oil pressure gauge, coolant temperature gauge, fuel gauge, and voltage
gauge. It also has a series of warning indicator lamps to provide the driver with all the necessary information to ensure that the vehicle is in perfect
operating condition.
The electronic instrument cluster receives virtually all of the information for its displays from the body controller and the engine controller via the
CCD bus system.
The electronic instrument cluster has two forms of diagnostic routines that are used to isolate problems within the cluster. Self-diagnostics use the
"TRIP" and "TRIP RESET" buttons for access, and CCD bus diagnostic routines require the use of the DRBII diagnostic readout box.
Successful completion of the self-diagnostic test indicates that the problem is in the CCD bus, interfacing modules, connectors, wiring harnesses, or
sensors outside the cluster.
The body controller (not the electronic instrument cluster) stores the odometer information that is displayed on the instrument cluster. Therefore, when
replacement of the electronic cluster is required, the odometer reading will not be affected.
EVIC Head Monitor
The Electronic Vehicle Information Center (EVIC) module is located in the overhead console. It displays to the driver such information as time,
outside temperature, compass direction, and fuel economy.
