CTS-V V8-6.0L VIN U (2006)
Body Control Module: Description and Operation
Body Control System
BODY CONTROL SYSTEM DESCRIPTION AND OPERATION
The body control system consists of the following 2 modules:
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The dash integration module (DIM)
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The rear integration module (RIM)
Each of the 2 body control modules integrate a number of functional systems. Each module is connected to the class 2 serial data circuit, many of the
control signals are implemented by class 2 messages.
Dash Integration Module (DIM)
The various dash integration module (DIM) input and output circuits are described in the corresponding functional areas as indicated on the DIM
electrical schematics.
The DIM functions include the following:
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The cigar lighter relay control
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The class 2 communication requiring DIM interaction
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The exterior lighting control
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The headlamp washer control
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The hood ajar switch input w/export
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The horn relay control
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The interior lighting control
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The load management
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The low side temperature for HVAC compressor
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The park key lock output
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The power moding control over class 2 serial data circuit
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The reverse lockout solenoid control
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The steering wheel controls input
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The storage of the clock settings and, sending a message out on the class 2 serial data circuit in response to requests from other modules
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The storage of vehicle options and configuration
Power Mode
The dash integration module (DIM) is the power mode master (PMM). Refer to Power Mode Description and Operation for more information.
Fail-Safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the power mode master (PMM) fail to
send a power mode message. The fail-safe plan covers those modules using exclusively serial data control of power mode as well as those modules
with discrete ignition signal inputs.
Serial Data Messages
The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid PMM message until they can
check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag
serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state the modules and
their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules
fail-safe to OFF-AWAKE. In this state, the modules are constantly checking for a change status message on the serial data circuits and can respond to
both local inputs and serial data inputs from other modules on the vehicle.
Discrete Ignition Signals
Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid PMM message received on the serial data
circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, battery
positive voltage, the modules will fail-safe to the RUN power mode. If the discrete ignition input is not active, open, or 0 voltage, the modules will
fail-safe to OFF-AWAKE. In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to
both local inputs and serial data inputs from other modules on the vehicle.
Electrical Load Management
The power management function is designed to monitor the vehicle electrical load and determine when the battery is potentially in a high discharge
condition. This is accomplished by using a high accuracy battery voltage reading as an indicator of battery discharge rate. The following 6 levels of
load management will execute in the load management control algorithm when there is a high discharge condition:
1. The first action requests a vehicle idle speed increase to the engine control module (ECM) in order to raise alternator output.
2. The second action requests a greater vehicle idle speed increase to the ECM in order to raise alternator output.
3. The third action begins to shed vehicle loads in an attempt to remedy the heavy discharge condition.
4. The fourth action requests another vehicle idle speed increase to the ECM in order to raise further the alternator output.
5. The fifth action begins to shed further vehicle loads in an attempt to remedy the heavy discharge condition.
