Body Control Systems: Description and Operation

BODY CONTROL SYSTEM DESCRIPTION AND OPERATION

The body control module (BCM) has a bussed electrical center integrated into the housing. Body control relays and fuses are installed directly on the BCM, which simplifies wiring and junction blocks on the vehicle. The body control system consists of the BCM and its associated controls. Battery positive voltage is provided to the BCM from IBCM BATT 1 fuse and the IBCM BATT 2 fuse in the underhood fuse block. The module grounds are wired to ground G201, G203 and G305. The BCM is wired to the GMLAN High speed serial data buss, and the GMLAN Low speed serial data buss, as well as discrete input and output terminals to control the functions of the vehicle's body.

SERIAL DATA GATEWAY
The body control module (BCM) in this vehicle functions as a translator between the High and Low speed GMLAN busses. The 2 communication protocols use the BCM to translate communicated serial data messages between the control modules over the 2 serial data busses.

POWER MODE MASTER
This vehicles body control module (BCM) functions as the power mode master (PMM). Refer to Power Mode Description and Operation for a complete description of power mode functions.

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. The BCM functions include the following:
- A/C compressor request-Refer to Theft Systems Description and Operation for the manual system.
- A/C cooling fan-Refer to Air Delivery Description and Operation for the manual system.
- Battery rundown protection (inadvertent power)-Refer to Interior Lighting Systems Description and Operation.
- Bulb check-Refer to Instrument Cluster Description and Operation.
- Chimes-Refer to Indicator/Warning Message Description and Operation.
- Check gages
- Door ajar warning
- Headlamps ON
- Key-in-ignition
- Oil reset
- Park brake warning
- Seat belt not fastened
- Turn signal ON

- Door lock interface-Refer to Power Door Locks Description and Operation.
- Electronic power steering (EPS)-Refer to Power Steering System Description and Operation.
- Engine coolant level sensing-Refer to Cooling System Description and Operation.
- Exterior and interior lighting control-Refer to Exterior Lighting Systems Description and Operation.
- Automatic lighting control
- Daytime running lamps (DRL)
- Fog lamps
- Park brake lights
- Turn hazard lamps

- Gage control-Refer to Instrument Cluster Description and Operation.
- Horn interface-Refer to Horns System Description and Operation.
- Instrument cluster indicator control-Refer to Instrument Cluster Description and Operation.
- Interior lighting-Refer to Interior Lighting Systems Description and Operation.
- Key-in-ignition sensing-Refer to Indicator/Warning Message Description and Operation.
- Parking brake state sensing-Refer to Brake Warning System Description and Operation.
- Retained accessory power (RAP)-Refer to Retained Accessory Power (RAP) Description and Operation.
- Rear compartment interface-Refer to Power Door Locks Description and Operation.
- Rear defogger-Refer to Rear Window Defogger Description and Operation.
- Remote function control-Refer to Keyless Entry System Description and Operation.
- Seat belt use sensing-Refer to Seat Belt System Description and Operation.
- Content theft deterrent-Refer to Theft Systems Description and Operation.
- Vehicle theft deterrent-Refer to Theft Systems Description and Operation.
- Washer solvent level sensing-Refer to Wiper/Washer System Description and Operation (Front) Wiper/Washer System Description and Operation (Rear).
- Wiper/washer-Refer to Wiper/Washer System Description and Operation (Front) Wiper/Washer System Description and Operation (Rear).