GM Service Manual Online
For 1990-2009 cars only

The body control system consists of a BCM and it's associated controls. Battery positive voltage is provided to the BCM from BFC/BATT fuse in the left hand Instrument panel fuse block. The module ground is wired to ground G202. The BCM utilizes inputs Ignition 0, Ignition 1 and Ignition 3 to differentiate the power mode that the ignition switch has bean placed in. The other Subsystems also use these three ignition lines to identify which power mode they should be operating in. The engine run flag is used by the vehicle subsystems to continue operating fail enable in the event one of the necessary ignition signals malfunction during the Run power mode. The BCM is wired to the Class 2 serial data communication bus as well as discreet input and output terminals to control the functions of the vehicles body . The various BCM input and output circuits are described in the corresponding functional areas indicated on the BCM electrical schematics. The Body Control Module functions include the following:

    • A/C compressor request. Refer to Air Temperature Description and Operation
    • Remote Function Control. Refer to Keyless Entry System Description and Operation
    • A/C cooling Fan. Refer to Air Delivery Description and Operation
    • Exterior and interior lighting control. Refer to Exterior Lighting Systems Description and Operation
       - Daytime running lights (DRL)
       - Automatic lighting control
       - Fog lamps
    • Interior lighting. Refer to Interior Lighting Systems Description and Operation
    • Battery rundown protection (Inadvertent Power). Refer to Interior Lighting Systems Description and Operation
    • Chimes. Refer to Audible Warnings Description and Operation
       - Key-In-Ignition
       - Head Lamps On
       - Seat Belt Not Fastened
       - Turn Signal On
       - Park Brake Warning
       - Door Ajar Warning
       - Check gages
    • Gage control. Refer to Instrument Cluster Description and Operation
    • Instrument cluster indicator control. Refer to Instrument Cluster Description and Operation
    • Theft deterrent. Refer to Theft Systems Description and Operation
    • Engine coolant level sensing. Cooling System Description and Operation
    • Washer solvent level sensing. Refer to Wiper/Washer System Description and Operation
    • Key-in-ignition sensing. Refer to Audible Warnings Description and Operation
    • Seat belt use sensing. Refer to Seat Belt System Description and Operation
    • Brake fluid level sensing. Refer to Brake Warning System Description and Operation
    • Parking brake state sensing. Refer to Brake Warning System Description and Operation
    • Rear compartment interface. Refer to Power Door Locks Description and Operation
    • Horn interface. Refer to Horns System Description and Operation
    • Door lock interface. Refer to Power Door Locks Description and Operation
    • Bulb Check. Refer to Instrument Cluster Description and Operation