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.