The Controller Area Network (CAN) data bus system is a multiplex system used for vehicle communications. Mul-
tiplexing 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.

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OPERATION

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 capac-
itor. 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 mod-
ulation 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.

DATA LINK CONNECTOR

DESCRIPTION

The Data Link Connector (DLC) (1) is located at the lower edge of the instrument panel (3) near the hood release
(2). The exposed connector terminals are protected by a plastic cover which flips open if access is needed.

OPERATION

The 16-way Data Link Connector (DLC) provides a communication link between the DRB III

scan tool and the

vehicle electronic control modules.

ELECTRONIC CONTROL MODULES - SERVICE INFORMATION

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POWERTRAIN CONTROL MODULE

DESCRIPTION

The Powertrain Control Module (1) is concealed in the engine compartment inside the Control Module Box (2)
located next to the Battery (3).

The Powertrain Control Module utilizes integrated circuitry and information carried on the Controller Area Network
(CAN) data bus along with many hard wired inputs to monitor many sensor and switch inputs throughout the vehi-
cle. In response to those inputs, the internal circuitry and programming of the Powertrain Control Module allow it to
control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the
transmission of electronic message outputs to other electronic modules in the vehicle over the CAN data bus.

The Powertrain Control Module for this model is serviced only as a complete unit. A Powertrain Control Module can
only be repaired by, or replaced through an authorized electronic warranty repair station. Refer to the latest version
of the warranty policies and procedures manual for a current listing of authorized electronic repair stations.

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