General Description

PURPOSE
The body system consists of a combination of modules that communicate over the Chrysler Collision Detection (CCD) multiplex system bus. Through the CCD bus, information about the operation of vehicle components and circuits is relayed to the appropriate module(s). Each module receives the same information about a component or circuit as the other modules do. This significantly reduces the complexity of the wiring in the vehicle and the size of the wiring harnesses.

OPERATION
The CCD bus consists of a twisted pair of wires. These wires run from one module to another. They receive and deliver coded information between the modules. The information is coded to identify the message as well as the importance of the message. When there are multiple messages trying to access the CCD bus at one time, the code determines which message has a higher priority, and which 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) respectively. Each wire has a measurable voltage level of roughly 2.5 volts. In order to maintain 2.5 volts on each line and provide a means of transportation of the coded messages, there is a "voltage divider network". This network consists of some modules with bias and some with termination. Bias is the part of the voltage divider network that places both bus + and bus - at 2.5 volts. Termination of the circuitry is required to complete the voltage divider network and also to provide some electromagnetic protection for the bus.

NOTE: Communication over the bus is essential to the proper operation of the vehicles' on-board diagnostic systems and the Diagnostic Readout Box (DRB). Problems with the operation of the bus or DRB must be corrected before proceeding with diagnostic testing.