GM Service Manual Online
For 1990-2009 cars only

Power Requirements

The BCM has three main voltage feeds and three grounds. The voltage feed circuits are used to provide power for the BCM's logic, courtesy lights, internal driver operation and the door locks.

BCM Inputs

The following components provide direct input to the BCM, plus other systems can use this input information in order to carry out certain functions:

    • Accessory Signal Input: Provides accessory power for the BCM.
    • Battery Power: Provides the BCM power for the door locks.
    • BCM Ground: Provides ground for BCM operation.
    • BCM Power: Provides voltage for BCM operation.
    • Courtesy Lights On Input: Determines when the dome lamp switch (Headlamp Switch) is closed to request the dome lamp on.
    • Crank Signal: Determines when the ignition switch is in the start position.
    • Door Lock Switch: Door lock switch request to lock the vehicle doors.
    • Door Open: Provides door ajar status.
    • Door Relay Ground: Provides the BCM, internal door relays, with ground.
    • Door Unlock Switch: Door lock switch request to unlock the vehicle doors.
    • Driver Door Open: Allows certain chime functions when the driver's door is open.
    • Driver Seat Belt Unfastened Input: Determines when the driver seat belt is unfastened.
    • DRL Signal Low: This input provides the BCM with Information through an ambient light sensor for the DRL feature.
    • Exterior Lamps Off Inpt: Determines when the headlamp switch is in the OFF position.
    • Ground: Provides the Steering Column Lock And Ignition Key Cylinder with ground.
    • Headlamp Switch Input: Determines when the Headlamp relay is energized
    • Ignition 0 Signal: Determines when the ignition switch is in theOFF, RUN or START position.
    • Ignition 1 Signal: Determines when the ignition switch is in the RUN or START positions.
    • Key In Ignition: Determines when the key is fully inserted in the ignition key cylinder.
    • Key Read: Provides the BCM with Passkey information.
    • Left Turn Switch: Determines if the Left Turn Switch has been activated.
    • Park Brake Applied Input: Determines when the parking brake is applied.
    • Performance Shift Switch Input: Determines if the Performance Shift Switch has been switched.
    • Rear Compartment Ajar: Determines if the rear decklid is open or closed.
    • RFA Link: Provides an interface allowing the transfer of keyless entry information from the Remote Control Door Lock Receiver (RCDLR).
    • Right Turn Switch: Determines if the Right Turn Switch has been activated.
    • Serial Data Class 2: Provides an interface with the PCM, EBCM, Heater A/C Control, SDM and the IPC through the Class 2 serial data link.
    • Theater Dimming 1 Ground: Provides ground for Theater Dimming 1 control.
    • Tire Inflation Reset Switch Input: Provides the BCM with a momentary switch to ground to request a Tire Inflation Reset.
    • Traction Control Request: This input provides the BCM with a request for Traction Control through a momentary switch connected to ground.

BCM Outputs

The BCM directly controls these outputs, plus other systems may request the BCM to control these outputs for certain functions:

    • All Door Lock: This output supplies voltage to the door lock actuators when the doors are commanded to lock. This output also supplies ground to all the door lock actuators when the doors are commanded to unlock.
    • Back Up Lamp Relay Control: Provides ground to the back up lamp relay control ciruit.
    • Courtesy Lamps Switched Feed: Provides courtesy lamps with power.
    • Driver Door Unlock: This output supplies voltage to the driver door lock actuators when the doors are commanded to unlock. This output also supplies ground to the driver door lock actuator when the doors are commanded to lock.
    • DRL 5V Reference: Provides 5 volts to the ambient light sensor.
    • DRL Link: Provides ground to the Headlamp relay control ciruit.
    • Fog Lamp Enable: Sends a ground signal to the fog lamp switch when the ignition switch is on, this action enables the fog lamp switch. The fog lamps turn on when the fog lamp switch is enabled by the BCM.
    • Horn: Sends a ground signal to the horn relay, sounding the horn for the keyless entry alarm function or the content theft system.
    • Park Lamp Relay Control: Provides ground to the Park Lamp relay control ciruit.
    • Passenger Door Unlock: This output supplies voltage to the door lock actuators (except the driver door lock actuator) when the doors are commanded to unlock. This output also supplies ground to all the door lock actuators (except the driver door lock actuator) when the doors are commanded to lock.
    • RAP Relay Control: Provides ground to the RAP relay control ciruit.
    • Rear Compartment Lid Release Relay Control: Provides ground to the Rear Compartment Lid Release Relay control ciruit.
    • RFA Link: Provides an interface allowing the transfer of keyless entry information to the Remote Control Door Lock Receiver (RCDLR).
    • Theater Dimming 1Control: Supplies ground to activate the interior lamps.