Body Control Module: Operation

The Body Control Module (BCM) monitors many hard wired switch and sensor inputs as well as those resources it shares with other electronic modules in the vehicle through its communication over the Programmable Communications Interface (PCI) data bus network. The internal programming and all of these inputs allow the BCM microprocessor to determine the tasks it needs to perform and their priorities, as well as both the standard and optional features that it should provide. The BCM programming then performs those tasks and provides those features through both PCI data bus communication with other electronic modules and through hard wired outputs through a number of driver circuits, relays, and actuators. These outputs allow the BCM the ability to control numerous accessory systems in the vehicle.

The BCM operates on battery and ignition voltage inputs received through several fuses in the Junction Block (JB). This arrangement allows the BCM to provide some features regardless of the ignition switch position, while other features will operate only with the ignition switch in the On, Start, and/or Accessory positions. All of the battery voltage circuits are connected to the BCM through the JB/BCM connector. The BCM receives ground through five separate circuits. Three of these circuits are connected to the BCM through a connector of the instrument panel wire harness on three separate ground circuits, while the other two circuits are connected to the BCM through the JB/BCM connector.

The BCM monitors its own internal circuitry as well as many of its input and output circuits, and will store a Diagnostic Trouble Code (DTC) in electronic memory for any failure it detects. These DTCs can be retrieved and diagnosed using a DRBIII(R) scan tool. Refer to the appropriate diagnostic information.

HARD WIRED INPUTS The hard wired inputs to the BCM include the following:

A/C On/Off Control
Door Lock Switch
Driver Door Ajar Switch Sense
Flip-Up Glass Ajar Switch Sense
Flip-Up Glass Release Switch Sense
Fog Lamp Switch Sense
Front Wiper Park Switch Sense
Front Wiper Switch
Front Washer Pump Driver
Fused B(+)
Fused Ignition Switch Output (Run-Acc)
Fused Ignition Switch Output (Run-Start)
Headlamp Switch
High Beam Switch Sense
Hood Ajar Switch Sense - Premium With VTSS - Markets Where Required Only
Key-In Ignition Switch Sense
Left Cylinder Lock Switch Sense - Premium With VTSS Only - Omitted In Some Markets As Required
Panel Lamps Dimmer Switch
Passenger Doors Ajar Switch Sense (Input From Three Ajar Switches Connected In Parallel)
Radio Control - Premium With Remote Radio Switches Only
Rear Courtesy Lamp Control
Rear Window Defogger Control
Rear Wiper Intermittent Driver
Rear Wiper On Driver
Right Cylinder Lock Switch Sense - Premium With VTSS Only - Omitted In Some Markets As Required
RKE Antenna (Two Circuits) - Premium With RKE Only
Tailgate Ajar Switch Sense
Tailgate Cylinder Lock Switch Sense
Vehicle Speed Sensor Signal