Component Description

Fig.1 Body Control Module:

BODY CONTROL/CENTRAL TIMER MODULE
The Body Control Module (BCM) is concealed below the driver side end of the instrument panel in the passenger compartment, where it is secured to the dash panel side of the Junction Block (JB) with four screws. The BCM is enclosed in a molded plastic housing with two integral external connector receptacles that connect it to the vehicle electrical system through two take outs with connectors from the instrument panel wire harness. The BCM also has an integral interface connector concealed on the back side of the unit that joins it through a connector receptacle that is integral to the JB housing to the circuitry within the JB. Two locator channels or ramps molded into the lower edge of the BCM housing are designed to guide the mounting latches of the instrument panel fuse cover to the two mounting slots in the lower forward-facing surface of the BCM housing.

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:
- A/C Select Switch Status - The BCM monitors and transmits the status of the A/C switch on both manual heater-A/C and Automatic Zone Control (AZC) equipped vehicles.
- Accessory Delay Control - The BCM provides an accessory delay feature that allows operation of the power windows or power sunroof for a timed interval following ignition OFF.
- Ambient Temperature Data - The BCM monitors and transmits the ambient temperature sensor input data.
- Automatic Headlamps - The BCM monitors an ambient light sensor to provide an automatic head- lamps feature for vehicles equipped with this option.
- Cargo Lamp Disable - The BCM provides a cargo lamp disable feature.
- Chimes - The BCM provides chime service through an integral chime tone generator. This includes a programmable low fuel warning chime.
- Courtesy Lamps - The BCM provides courtesy lamp control with a theater-style fade-to-off feature and transmits the status of the system.
- Customer Programmable Features - The BCM provides support for the customer programmable features function of the Electronic Vehicle Information Center (EVIC).
- Exterior Lamp Load Shedding - The BCM provides a battery saver feature which will automatically turn OFF exterior lamps that remain ON after a timed interval.
- Exterior Lamp Status - The BCM monitors the status of the park lamp, head lamp, and fog lamp relays.
- Exterior Lighting Control - The BCM provides exterior lamp control for standard head and park lamps, as well as optional automatic headlamps, optional fog lamps, and Daytime Running Lamps (DRL) for vehicles sold in Canada.
- Fluid Level Status of Washer and Coolant Reservoirs - The BCM monitors and transmits the status of the washer fluid level switch and the coolant level sensor inputs.
- Fuel Economy and Distance to Empty Calculations - The BCM calculates and transmits the fuel economy and Distance To Empty (DTE) data.
- Gulf Coast Country Overspeed Warning - The BCM provides an audible overspeed warning feature used for vehicles sold in Middle East Gulf Coast Countries (GCC).
- Headlamps ON With Wipers - The BCM provides an automatic headlamps ON with wipers turned ON on feature for models with the optional automatic headlamps. This is a programmable feature.
- Headlamp Time Delay - The BCM provides a headlamp time delay feature with programmable delay intervals.
- Heated Rear Glass Control - The BCM provides control and timer functions for the heated rear glass feature and transmits the system status.
- Heated Seat Switch Status - The BCM monitors and transmits the status of both the driver and passenger heated seat switches.
- Ignition ON/OFF Timer - The BCM monitors and transmits the elapsed ignition ON timer data and monitors the ignition OFF time.
- Ignition Switch Position Status - The BCM monitors and transmits the status of the ignition switch.
- Illuminated Entry - The BCM provides a timed illuminated entry feature and transmits the system status.
- Instrument Panel Dimming - The BCM controls the illumination intensity of all instrument panel lighting.
- Intermittent Wipe and Low Speed Wiper Control - The BCM provides low speed front wiper system control with intermittent wipe, mist, and wipe-after-wash features.
- Key-In-Ignition Switch Status - The BCM monitors and transmits the status of the key-in-ignition switch (ignition switch).
- Panic Mode - The BCM provides support for the RKE system panic mode feature.
- Parade Mode - The BCM provides a parade mode (also known as funeral mode) that allows the interior Vacuum Fluorescent Displays (VFD) to be illuminated at full intensity while driving in daylight with the exterior lamps ON.
- Reading Lamp/Glove Box Lamp Load Shedding - The BCM provides a battery saver feature that will automatically turn OFF reading lamps or a glove box lamp that remain ON after a timed interval.
- Rear Door and Liftgate Ajar Status - The BCM monitors and transmits the status of the rear door, liftgate, and liftgate flip-up glass ajar switches.
- Rear Fog Lamp Control - The BCM provides control for the optional rear fog lamps used for vehicles sold in some markets.
- Remote Radio Switch Interface - The BCM monitors and transmits the status of the optional remote radio switches.
- Seat Belt Switch Status - The BCM monitors and transmits the status of the driver side front seat belt switch.
- Speed Sensitive Intermittent Wipe Control - The BCM provides the speed sensitive intermittent wipe feature.
- Vacuum Fluorescent Display Synchronization - The BCM transmits panel lamp intensity data which allows Vacuum Fluorescent Display (VFD) modules to coordinate their lighting intensity.
- Vehicle Theft Alarm - The BCM provides control of the optional Vehicle Theft Alarm features.
- Wiper System Status - The BCM monitors the front wiper motor park switch status.

Hard wired circuitry connects the BCM to the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the BCM through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

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. However, if any of the BCM hardware components is damaged or faulty, the entire BCM unit must be replaced. 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 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 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 low current 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, while other features will operate only with the ignition switch in the Accessory, ON, and/or Start positions. The BCM circuitry is grounded through five separate ground circuits, three located in the BCM C1 connector and take out of the instrument panel wire harness, and two located in the JB C3 connector and take out of the instrument panel wire harness. These ground circuits receive ground through a single wire take out with an eyelet terminal connector of the instrument panel wire harness that is secured by a nut to a ground stud located on the floor panel transmission tunnel beneath the center floor console, just forward of the Airbag Control Module (ACM).

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

Hard Wired Outputs
The hard wired outputs of the BCM include the following:
- Ambient temperature sensor return
- Courtesy lamp driver (three circuits - two M2,and one M20)
- Courtesy lamp load shed
- Fog lamp relay control
- Headlamp switch return
- High beam relay control
- Horn relay control-Low beam relay control
- Panel lamps driver (five circuits)
- Park lamp relay control
- Park lamp relay output
- PCI bus
- Radio control mux return
- Rear window defogger relay control
- Seat heater switch sensor ground
- Sunroof delay relay control
- VTSS indicator driver
- Ultralight sensor return
- Windshield wiper switch return
- Wiper ON/OFF relay control

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/OFF 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)