GM Service Manual Online
For 1990-2009 cars only

The body control module (BCM) controls a number of functional systems. The BCM is connected to the Class 2 serial data line. Many control signals are implemented by Class 2 messages.

The BCM functions include the following:

    • Ajar switch and tamper switch inputs from the rear compartment lid
    • Auxiliary chime control
    • Control of headlights and exterior lamps
    • Heated seat controls
    • IP dimmer switch input
    • Interior lamps incandescent dimming
    • Interior lamps switch input
    • Key-in-ignition switch input from the ignition switch
    • Low coolant sensor input
    • Power moding control (ignition switch states) over Class 2 serial data line
    • Rear compartment lid release control
    • Rear defogger control
    • Retained accessory power (RAP) control
    • Seatbelt reminder/warning control
    • Steering wheel controls
    • Traction control switch input
    • Various controls for the interior lamps