Crossfire SRT-6 V6-3.2L SC VIN N (2005)
Information Bus: Description and Operation
The Controller Area Network (CAN) data bus system is a multiplex system used for vehicle communications. Multiplexing is a system that enables the
transmission of several messages over a single channel or circuit.
Many of the control modules in a vehicle require information from the same sensing device. Multiplexing reduces wire harness complexity, sensor
current loads and controller hardware because each sensing device is connected to only one controller, which reads and distributes the sensor information
to the other controllers over the data bus. Also, because each controller on the data bus can access the controller sensor inputs to every other controller
on the data bus, more function and feature capabilities are possible.
A multiplex system allows the information flowing between controllers to be monitored using a diagnostic scan tool. This system allows a control
module to broadcast message data out onto the bus where all other control modules can read the messages that are being sent. When a module reads a
message on the data bus that it requires, it relays that message to its microprocessor. Each module ignores the messages on the data bus that it does not
recognize.
Data exchange between modules is achieved by serial transmission of encoded data over a broadcast network. The Controller Area Network (CAN) data
bus messages are carried over the bus in the form of variable pulse width modulated signals. The Engine CAN C Data Bus speed is 500 Kilo-bits per
second (Kbps) (ignition on) while the Interior CAN B Data Bus speed is 83 Kilo-bits per second (Kbps).
The voltage network used to transmit messages requires biasing and termination. The biasing and termination for the network is supplied by the PCM
and the SKREEM Module with a terminating resistor and a terminating capacitor. The Powertrain Control Module is the dominant node for the CAN C
Engine Data Bus System and the Body Control Module is the dominant node for the CAN B Interior Data Bus System.
The CAN bus uses low and high voltage levels to generate signals. The voltage on the bus varies between zero and two and one-half volts. The low
and high voltage levels are generated by means of variable-pulse width modulation to form signals of varying length.
When a module is transmitting on the bus, it is reading the bus at the same time to ensure message integrity.
