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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 GMLAN high speed serial data buss and the GMLAN low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine control module (ECM)/powertrain control module (PCM) and theft deterrent module (TDM) to communicate without the BCM providing the gateway function.
Power Mode Master
This vehicles 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 determination the power mode that will be sent over the serial data circuits to the other modules that need this information, and so the PMM will activate relays and other direct outputs of the PMM as needed.
Serial Data 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 buss and the GMLAN low speed buss for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.
One example of this necessary communication is the communication between the engine control module (ECM)/powertrain control module (PCM) which is high speed serial data and Theft Deterrent Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.
Communication between the BCM and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.
Body Control Module
The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. Some BCM functions with the subsystems may be as a gateway only or as an enable for the system. The BCM related systems/subsystems include, but are not limited to the following:
? Antilock Brake System (ABS)
? Automatic Day-Night Mirror
? Cruise Control System
? Electrical Power Management (EPM)
? Exterior Lighting
? Horn System
? HVAC
? Instrument Cluster Indicator Control
? Interior Lighting
? Power Door Lock System
? Rear Window Defogger System
? Redundant Steering Wheel Controls
? Remote Function Actuation (RFA) Control
? Retained Accessory Power (RAP)
? Shift Lock Control System
? Starting System
? Supplemental Inflatable Restraint (SIR) System
? Suspension System
? Theft Deterrent
? Tire Pressure Monitor (TPM) System
? Wiper/Washer System Functions
(1) I/P Trim
(2) I/P Cluster Trim
(3) Floor Panel
(4) Junction Block - Left I/P
(5) Body Control Module (BCM)
(6) Transfer Case Shift Control Module (NP
(7) Fuse Block - I/P
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 GMLAN high speed serial data buss and the GMLAN low speed serial data buss and acts as a gateway between them. If the BCM does not communicate the vehicle will not start due to the inability of the engine control module (ECM)/powertrain control module (PCM) and theft deterrent module (TDM) to communicate without the BCM providing the gateway function.
Power Mode Master
This vehicles 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 determination the power mode that will be sent over the serial data circuits to the other modules that need this information, and so the PMM will activate relays and other direct outputs of the PMM as needed.
Serial Data 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 buss and the GMLAN low speed buss for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.
One example of this necessary communication is the communication between the engine control module (ECM)/powertrain control module (PCM) which is high speed serial data and Theft Deterrent Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.
Communication between the BCM and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.
Body Control Module
The various body control module (BCM) input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. Some BCM functions with the subsystems may be as a gateway only or as an enable for the system. The BCM related systems/subsystems include, but are not limited to the following:
? Antilock Brake System (ABS)
? Automatic Day-Night Mirror
? Cruise Control System
? Electrical Power Management (EPM)
? Exterior Lighting
? Horn System
? HVAC
? Instrument Cluster Indicator Control
? Interior Lighting
? Power Door Lock System
? Rear Window Defogger System
? Redundant Steering Wheel Controls
? Remote Function Actuation (RFA) Control
? Retained Accessory Power (RAP)
? Shift Lock Control System
? Starting System
? Supplemental Inflatable Restraint (SIR) System
? Suspension System
? Theft Deterrent
? Tire Pressure Monitor (TPM) System
? Wiper/Washer System Functions
(1) I/P Trim
(2) I/P Cluster Trim
(3) Floor Panel
(4) Junction Block - Left I/P
(5) Body Control Module (BCM)
(6) Transfer Case Shift Control Module (NP
(7) Fuse Block - I/P