Durango 4WD V8-5.9L VIN Z (1998)
Body Control Module: Initial Inspection and Diagnostic Overview
Chrysler Collision Detection Multiplex System (CCD Bus)
The Chrysler Collision Detection multiplex system (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 the message that has the highest priority, and is then
allowed to access the bus first.
The two wires 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 the 2.5 volts on each line and provide a means of transportation for the coded
messages, there is a "voltage divider network" located in the module that supplies bus bias or voltage. Along with the module that supplies bias, some
modules provide termination. Bias is the voltage necessary to make the bus operational. At least one point of termination is necessary, some systems may
use more than one. Some modules are capable of both biasing and terminating. Termination in the circuitry (a 120 ohm resistor placed across the bus) is
required to complete the voltage divider network circuit and also provide some electromagnetic protection for the bus. In this vehicle, the bias is supplied
by the instrument cluster and termination is provided by the PCM. Without termination, voltage on the bus goes to approximately 5 volts on one wire and
0 volts on the other wire.
NOTE: Communication over the bus is essential to the proper operation of the vehicle's on-board diagnostic systems and the DRB. Problems with the
operation of the bus or DRB must be corrected before proceeding with diagnostic testing. If there is a problem, refer to Vehicle Communication Test 1A.
Bus Failure Messages
Short to Battery
Either or both of the bus wires are shorted to the battery potential.
Short to 5 Volts
Either or both of the bus wires are shorted to a 5-volt potential.
Short to Ground
Either or both of the bus wires are shorted to ground.
Bus (+) & Bus (-) Shorted Together
The two bus wires are shorted together.
No Termination
The bus system has lost connection with all of its terminators.
Bus Bias Level Too Low
Either of both of the bus wire potentials are significantly below their normal 2.5 volts.
Bus Bias Level Too High
Either of both of the bus wire potentials are significantly above their normal 2.5 volts.
No Bus Bias
The bus system has lost connection with all modules that provide bias.
Bus (+) Open
The bus (+) wire has lost connection with termination and/or bias.
Bus (-) Open
The bus (-) wire has lost connection with termination and/or bias.
Not receiving Bus Messages Correctly
The DRB cannot communicate over the bus and does not know why.
Bus Failure Messages
Bus Failure Messages
Short to Battery
Either or both of the bus wires are shorted to the battery potential.
Short to 5 Volts
Either or both of the bus wires are shorted to a 5-volt potential.
Short to Ground
Either or both of the bus wires are shorted to ground.
Bus (+) & Bus (-) Shorted Together
The two bus wires are shorted together.
No Termination
The bus system has lost connection with all of its terminators.
Bus Bias Level Too Low
Either of both of the bus wire potentials are significantly below their normal 2.5 volts.
Bus Bias Level Too High
Either of both of the bus wire potentials are significantly above their normal 2.5 volts.
No Bus Bias
The bus system has lost connection with all modules that provide bias.
Bus (+) Open
The bus (+) wire has lost connection with termination and/or bias.
