Body Control System Description and Operation
The body control system consists of the body control module
(BCM), communications, and various input and outputs. Some inputs,
outputs and messages require other modules to interact with the
BCM. The BCM also has discrete input and output terminals to
control the vehicle's body functions. The BCM is wired to the high
speed GMLAN serial data bus, low speed GMLAN serial data bus and
Multiple LIN buses and acts as a gateway between them.
Power Mode Master
This vehicle body control module (BCM) functions as the power
mode master (PMM). The ignition switch is a low current switch with
multiple discrete ignition switch signals to the PMM for
determining the power mode that will be sent over the serial data
circuits to the other modules that need this information; the PMM
will activate relays and other direct outputs of the PMM as needed.
Refer to
Power Mode Description and Operation for a complete description
of power mode functions.
Gateway
The body control module (BCM) in this vehicle functions as a
gateway or translator. The purpose of the gateway is to translate
serial data messages between the GMLAN high speed bus and the GMLAN
low speed bus for communication between the various modules. The
gateway will interact with each network according to that network's
transmission protocol.
All communication between the BCM and a scan tool is on the high
speed GMLAN serial data circuits. A lost communication DTC
typically is set in modules other than the module with a
communication failure.
Body Control
The various body control module (BCM) input and output circuits
are illustrated in the corresponding functional areas on the BCM
electrical schematics. Refer to the
Body Control System Schematics for more detailed
information.
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