Component Description

Fig.2 Body Control Module:

BODY CONTROL MODULE
A Body Control Module (BCM) is concealed below the driver side end of the instrument panel.

The BCM utilizes integrated circuitry and information carried on the Programmable Communications Interface (PCI) data bus network along with many hard wired inputs to monitor many sensor and switch inputs throughout the vehicle. In response to those inputs, the internal circuitry and programming of the BCM allow it to control and integrate many electronic functions and features of the vehicle through both hard wired outputs and the transmission of electronic message outputs to other electronic modules in the vehicle over the PCI data bus. The electronic functions and features that the BCM supports or controls include the following:

The BCM for this model is serviced only as a complete unit. Many of the electronic features in the vehicle controlled or supported by the BCM are programmable using either the Electronic Vehicle Information Center (EVIC) user interface, or the DRB III scan tool. In addition, the BCM software is Flash compatible, which means it can be reprogrammed using Flash reprogramming procedures. A BCM can only be repaired by or replaced through an authorized electronic warranty repair station. Refer to the latest version of the Warranty Policies and Procedures manual for a current listing of authorized electronic repair stations.

The Body Control Module (BCM) is designed to control and integrate many of the electronic features and functions of the vehicle. The microprocessor based BCM hardware and software 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 PCI data bus network. The internal programming of the BCM microprocessor allows the BCM to determine the tasks it needs to perform and their priorities. The BCM programming then performs those tasks and provides features through both PCI data bus communication with other electronic modules and hard wired outputs to a number of relays. These relays provide the BCM with the ability to control numerous high current accessory systems in the vehicle.

The BCM circuitry operates on battery current received through fuses in the Junction Block (JB) on a non-switched fused B(+) circuit, a fused ignition switch output (start-run) circuit, and a fused ignition switch output (run-accessory) circuit. This arrangement allows the BCM to provide some features regardless of the ignition switch position. The BCM circuitry is grounded through the chassis beneath the center console.

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 DRB III scan tool. Refer to the appropriate diagnostic information.

Hard Wired Inputs
The hard wired inputs to the BCM include the following:
- A/C switch signal
- Ambient temperature sensor signal
- Body control module flash enable
- Coolant level switch sense
- Door ajar switch sense (two circuits - one left rear, and one right rear)
- Driver seat heater switch mux
- Fog lamp switch sense
- Fused B(+)
- Fused ignition switch output (run-acc)
- Fused ignition switch output (st-run)
- Ground (five circuits - two Z1, and three Z2)
- Hazard switch sense
- Headlamp switch mux
- High beam switch sense
- Hood ajar switch sense (export)
- Key-in ignition switch sense
- Liftgate ajar switch sense
- Liftgate courtesy disable
- Liftgate flip-up ajar switch sense
- Panel lamps dimmer signal
- Park lamp relay output
- Passenger seat heater switch mux
- PCI bus
- Radio control mux
- Rear window defogger switch sense
- Seat belt switch sense
- Ultralight sensor signal
- Washer fluid switch sense
- Washer pump switch sense
- Windshield wiper switch mux
- Wiper park switch sense

Messaging
The BCM uses the following messages received from other electronic modules over the PCI data bus:
- Accessory Delay Control (DDM/PDM)
- Battery Temperature (PCM)
- Chime Request (EMIC, EVIC, SKIM)
- Cylinder Lock Switch Status (DDM)
- Door Ajar Status/Front Doors (DDM/PDM)
- Door Lock Status (DDM/PDM)
- Engine Model (PCM)
- Engine RPM (PCM)
- Engine Temperature (PCM)
- English/Metric Default (EMIC)
- Fuel Tank Level (PCM)
- Fuel Used/Injector Pulses (PCM)
- Panic Control (PDM)
- Programmable Features Preferences/Audible & Optical Chirps/Headlamp Delay (EVIC)
- RKE Status (PDM)
- Vehicle Identification Number (PCM)
- Vehicle Speed (PCM)

The BCM provides the following messages to other electronic modules over the PCI data bus:
- A/C Switch Status (PCM)
- Ambient Temperature Data (AZC/EVIC/PCM)
- Average/Instantaneous Fuel Economy (EVIC)
- Country Code (EMIC)
- Courtesy Lamp Status (DDM/PDM)
- Distance To Empty (EVIC)
- Elapsed Ignition On Timer (EVIC)
- English/Metric Status (EMIC)
- Front & Rear Door Ajar Status (EVIC)
- Front & Rear Fog Lamp Status (EMIC)
- Heated Seat Switch Status (HSM/MHSM)
- High Beam Status (EMIC)
- Ignition OFF Timer (EVIC)
- Ignition Switch Position (DDM/PDM)
- Key-In Ignition Status (DDM/PDM)
- Low Beam Status (EMIC)
- Panel Lamp Status (AZC/EMIC/Radio)
- Rear Window Defogger Relay Status (DDM/ PDM)
- Remote Radio Switch Status (Radio)
- Seatbelt Status (EMIC/MHSM/MSM)