Body Control Module: Operation

The Body Control Module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions. To provide and receive information, the BCM is interfaced to the vehicle's serial bus communications network, referred to as the Programmable Communications Interface (PCI) bus.

This network consists of the;

• Powertrain Control Module (PCM)
• Transmission Control Module (TCM)
• Mechanical Instrument Cluster (MIC)
• Occupant Restraint Controller (ORC)
• Compass/Mini-Trip Computer (CMTC)
• Electronic Vehicle Information Center (EVIC)
• Controller Antilock Brake (CAB)
• HVAC Control Module
• Sliding Door Control Modules (driver and passenger side doors)
• Power Liftgate Module (PLG)
• Audio system equipped with RAZ, RBU, RBK, and RBB radios.
• Side Impact Airbag Control Module (SIACM)
• Memory Seat Module (MSM)
• Sentry Key Immobilizer Module (SKIM)

The BCM is operational when battery power is supplied to the module.

The BCM provides the following features:

• Power Door Locks
• Automatic Door Locks
• Battery Protection - The BCM will automatically turn off all exterior lamps after 3 minutes, and all interior lamps after 15 minutes after the ignition is turned off, if they are not turned off by the driver.
• Chime Control
• Compass/Mini-Trip support.
• Interior Lighting (Courtesy/Reading Lamps)
• BCM Diagnostic Reporting
• Electronic Lift gate Release (with Power Door Locks)
• Exterior Lighting
• Headlamp Time Delay (with/without Automatic Headlamps)
• Illuminated Entry
• Fade to Off Interior Lamps - This feature dims the interior lighting (courtesy lamps) gradually if the BCM does not receive any new inputs that would cause the interior lamps to remain on.
• Pulse Width Modulated Instrument Panel Dimming
• Door Lock Inhibit - This feature disables the door lock functions if the key is in the ignition and either front door is ajar. Pressing the Remote Keyless Entry (RKE) lock/unlock button under these conditions result in normal lock/unlock activation.

The BCM has the ability to LEARN additional features in the vehicle, provided the appropriate switch input and PCI data bus messages are received. Refer to the LEARNED FEATURES table.

When replacing a BCM there are three modules available:

• Base
• Midline
• RG - Export

The Midline controller is used on vehicles that have Power Door Locks. If a vehicle is equipped with the Vehicle Theft Security System, the Midline controller becomes a Premium when the theft feature is enabled.

The BCM has internal diagnostic capability that assists in diagnosing the system error. When an OPEN or a SHORT circuit exists, the diagnostic tool can be used to read the BCM faults. The faults are very descriptive in identifying the appropriate feature that has faulted.

The only two faults that the BCM logs that conclude the replacement of a BCM are faults;

• # 01 - Internal BCM failure (replace BCM)
• # 1F - J1850 Internal Hardware Failure (replace BCM)

Otherwise the appropriate diagnostic procedures for each of the features should be taken when the BCM logs a fault.