GM Service Manual Online
For 1990-2009 cars only

BCM Functions

The body control module (BCM) is capable of accomplishing multiple body control functions. Components directly connected to the BCM are controlled by the BCM outputs. The BCM can control its outputs based on input information it obtains from sensors and switches that are directly connected to the BCM, or by receiving information from other vehicle systems connected to the class 2 serial data link. The BCM evaluates this information and controls certain body systems by commanding an output ON or OFF.

The BCM is also capable of commanding other vehicle systems to control functions that are not directly wired to and/or controlled by the BCM. The BCM accomplishes this task by sending specific messages on the class 2 serial data link. The vehicle system capable of performing such function will respond to the BCM message.

The BCM controls/monitors the following functions:

    • Audible warnings
    • Indicators control
    • Interior lighting
    • Exterior lighting
    • Power/automatic door locks
    • Keyless entry
    • Content theft deterrent
    • Personalization
    • Serial power modes
    • Electrical power management

Power Mode Master

This vehicles body control module (BCM) functions as the power mode master (PMM). Refer to Ignition and Start Switch Replacement .

Audible Warning

The body control module (BCM) provides the following audible control functions. Some audible control functions may be controlled by other systems through the class 2 serial data link:

    • Headlamp on reminder
    • Key in ignition reminder
    • Personalization mode
    • Delay locking indication
    • Keyless entry programming/diagnostic mode indication

Refer to Audible Warnings Description and Operation .

Indicator Control

The body control module (BCM) provides the following indicator control functions through the class 2 serial data circuits. Some indicator control functions may be controlled by other systems through the class 2 serial data link:

    • Door ajar
    • Liftglass/endgate ajar
    • Park brake
    • High beam
    • Park lamp malfunction
    • Service vehicle soon
    • Personalization mode
    • Security LED
    • Battery

Refer to Instrument Cluster Description and Operation and Indicator/Warning Message Description and Operation .

Interior Lighting

The body control module (BCM) provides the following interior lighting functions. Some interior control functions may be controlled by other systems through the class 2 serial data link:

    • Interior illumination control
    • Backlight/Illumination
    • Delayed illumination
    • Illumination on key cylinder unlock
    • Exit illumination
    • Illumination after air bag deployment
    • Keyless entry unlock illumination
    • Interior lighting personalization

Refer to Interior Lighting Systems Description and Operation for more information.

Exterior Lighting

The body control module (BCM) provides the following exterior lighting control functions. Some exterior lighting control functions may be controlled by other systems through the class 2 serial data link:

    • Headlamps
    • Daytime running lights (DRL)
    • Park lamps
    • Perimeter lighting
    • Front fog lamps
    • Exterior lighting personalization

Refer to Exterior Lighting Systems Description and Operation for more information.

Power/Automatic Door Locks

The body control module (BCM) provides the following power/automatic door lock control functions. Some door lock control functions may be controlled and/or sent by other systems through the class 2 serial data link:

    • All door unlock
    • All door lock
    • Last door closed locking
    • Lockout prevention
    • Lockout prevention override
    • Shift into PARK unlock
    • Shift out of PARK lock
    • Unlock after air bag deployment
    • Delayed locking
    • Delayed locking override
    • Power/automatic door lock personalization

Refer to Power Door Locks Description and Operation for more information.

Keyless Entry

The body control module (BCM) provides the following keyless entry control functions. Some keyless entry control functions may be controlled and/or sent by other systems through the class 2 serial data link:

    • Remote driver door unlock
    • Remote all door unlock
    • Remote all door lock
    • Remote activation verification
    • Remote alarm
    • Keyless entry personalization

Refer to Keyless Entry System Description and Operation for more information.

Content Theft Deterrent

The body control module (BCM) provides the following content theft deterrent control functions. Some content theft deterrent control functions may be controlled and/or sent by other systems through the class 2 serial data link:

    • Intrusion detection
       - Status of the doors and rear endgate
       - Lock cylinders
       - Rear liftglass
       - Power door locks
       - The keyless entry system
    • Intrusion notification
       - Security indicator LED
       - Flashes the headlamps
       - Sounds the horns
       - Disables fuel delivery to the engine
    • Content theft deterrent personalization

Refer to Content Theft Deterrent (CTD) Description and Operation for more information.

Personalization

The body control module (BCM) provides personalization of vehicle functions which allow BCM features to be personalized based on driver preferences. The following vehicle functions may be personalized:

    • Headlamp exit delay
    • Interior lighting delay
    • Interior lighting ON
    • Auto door lock/unlock
    • Delayed locking
    • Remote driver door unlock
    • Remote lock/unlock confirmation
    • Unlock feedback
    • Lock feedback

Refer to the following Personalization Description and Operation for more information on how to set personalized options.