GM Service Manual Online
For 1990-2009 cars only

This vehicle is equipped with a body control module (BCM) that performs multiple body control functions. The following vehicle systems are controlled by the BCM:

    • Audible warnings
       - Key in the ignition reminder
       - Fasten seat belt reminder
       - Driver information reminder
       - Turn signal reminder
       - Headlamps on reminder
       - Feature customization and diagnostics mode indication
       - Auxiliary chime functions (Instrument cluster)
       - Last door closed locking reminder
    • Inadvertent load monitoring
    • Fasten seat belt indicator control
    • Interior light illumination
    • Power door locks functions
    • Keyless entry system functions (with AU0)
    • Key cylinder lock
    • Retained Accessory Power (RAP)
    • Content theft deterrent system (with UA6)
    • Feature customization
    • Service Diagnostics

These systems are controlled by the BCM's outputs. The BCM controls its outputs based upon input information obtained from the sensors and switches that are directly connected to the BCM. The BCM evaluates the input information and controls the body systems by commanding an output on or off.

BCM Identification

This vehicle is equipped with 1 of 3 types of BCMs. The BCM type installed on this vehicle is based on the vehicle equipment, point of sale, and option content.

Refer to On-Board Diagnostic Features for more information on how to identify the BCM type installed by using the on-board diagnostic feature. The following identifies the functions and basic option content of all 3 BCM types:

BCM Type 2

BCM type 2 is the base BCM that provides all standard BCM functions.

BCM Type 3

BCM type 3 provides all of the features of the BCM type 2 plus keyless entry. Vehicles with RPO AU0 are equipped with a BCM type 3.

BCM Type 4

BCM type 4 provides all of the features of the BCM type 2 and type 3 plus content theft deterrent. Vehicles with RPO AU0 and UA6 are equipped with a BCM type 4.

BCM Function

BCM Type

Audible Warnings

Type 2, 3, 4

Inadvertent Load Monitoring

Type 2, 3, 4

Fasten Seat Belt Indicator Control

Type 2, 3, 4

Interior Light Illumination

Type 2, 3, 4

Auxiliary Chime Functions (IPC)

Type 2, 3, 4

Driver Information Reminder

Type 2, 3, 4

Key Cylinder Unlock

Type 2, 3, 4

Power Door Lock Functions

Type 2, 3, 4

Automatic Door Locks

Type 2, 3, 4

Feature Customization

Type 2, 3, 4

On-Board Diagnostics

Type 2, 3, 4

Retained Accessory Power (RAP)

Type 2, 3, 4

Keyless Entry

Type 3, 4

Key Cylinder Lock

Type 4

Content Theft Deterrent

Type 4

Interior Lighting

The BCM provides the following interior light functions:

    • Interior illumination
    • Delayed illumination
    • Exit illumination
    • Theatre dimming
    • Door key unlock illumination
    • Keyless entry unlock illumination
    • Inadvertent load (battery rundown) protection
    • Interior light feature customization
       - Delayed illumination (on/off)
       - Exit lighting (on/off)

Refer to the Interior Lights Circuit Description in Lighting for customization features.

Automatic Door Locks

The BCM provides the following automatic door lock functions:

    • Door key all doors unlock
    • Door key all doors lock
    • Last door closed locking
    • Lockout prevention
    • Ignition off unlock
    • Shift into PARK unlock
    • Shift out of PARK lock
    • Sliding door delayed locking
    • Door lock feature customization
       - Automatic door lock (on/off)
       - Automatic door unlock (on/off)
       - Last door closed lock (on/off)
       - Lockout prevention (on/off)

Refer to the Automatic Door Lock System Description in Doors for customization features.

Keyless Entry (BCM Type 3, 4)

The BCM provides the following keyless entry functions:

    • Driver door unlock
    • All doors unlock
    • All doors lock
    • Activation verification (horn and lights)
    • Content theft alarm
    • Keyless entry feature customization
       - Activation verification (lights/horn and lights/off)
       - Driver door unlock only (on/off)

Refer to the Keyless Entry System Circuit Description in Keyless Entry for more information.

Content Theft Deterrent (BCM Type 4)

The BCM provides the following content theft deterrent functions:

    • Intrusion detection
       - Doors
       - Lock cylinders
       - Liftgate
       - Sliding doors
       - Shock sensor
       - Power door lock switches
    • Intrusion notification
       - Flashes the exterior lights
       - Sounds the horn
       - Security LED
    • Content theft feature customization
       - Content theft deterrent system (on/off)
       - Power door lock switch arming (on/off)
       - Door key cylinder arm/disarm (on/off)
       - Shock sensor (on/off)
       - Remote arm/disarm only (on/off)

Refer to Vehicle Theft Deterrent (VTD) Description in Theft Deterrent for more information.

On-Board Diagnostic Mode

The Body Control Module (BCM) provides on-board diagnostics to assist in diagnosing BCM related malfunctions. The BCM has the following diagnostic capabilities when entering the on-board diagnostic mode:

    • Feature Customization
    • Displaying DTCs
    • Clearing DTCs
    • Input/Output Diagnostics

To access the on-board diagnostic mode, refer to On-Board Diagnostic Features .