Acclaim L4-153 2.5L SOHC Flex Fuel (1994)
Information Bus: Description and Operation
CCD Bus
PURPOSE:
The CCD bus relays information about the operation of vehicle components and circuits to the appropriate module(s).
OPERATION
The body system consists of a combination of modules that communicate over the Chrysler Collision Detection multiplex system (CCD bus).
Each module receives the same information about a component or circuit as the other modules do.
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This significantly reduces the complexity of the wiring in the vehicle and the size of the wiring harnesses.
The CCD Bus may be used for communication between the Vehicle Theft Alarm (VTA) module, instrument panel, scan tool, and the Powertrain
Control Module (PCM).
The CCD Bus is both an input and output from the Vehicle Theft Alarm (VTA) module. Circuit D1 is used for CCD (+) and circuit D2 is used for
CCD (-). These circuits are connected in with the data link connector and the Powertrain Control Module (PCM).
Bus Information is Coded
The CCD bus receives and delivers coded information between the modules.
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The information is coded to identify the message as well as the importance of the message.
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When there are multiple messages trying to access the CCD bus at one time, the message with higher priority is allowed to access the bus first.
Twisted Pair
CCD bus consists of a twisted pair of wires that run from one module to another.
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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.
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Each wire has a measurable voltage level of roughly 2.5 volts.
Voltage Divider Network Bias and Termination
In order to maintain the 2.5 volts on each line and provide a means of transportation for the coded messages, there is a "voltage divider network."
This network consists of some modules with bias and some with termination.
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Bias is the part of the voltage divider network that places both bus+ and bus- at 2.5 volts.
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Termination in the circuitry is required to complete the voltage divider network and also to provide some electromagnetic protection for the
bus.
NOTE: Modules using the CCD bus can be identified by accessing them through the CCD bus using a scan tool with the correct connector and
cartridge.
