Body Control Module: Operation

The Body Control Module (BCM) is operational when supplied with 12v battery power. The BCM controls various vehicle functions. It also supplies information to the instrument cluster to provide visual and audible information to the vehicle occupants. To provide and receive information, the module interfaces with the vehicle's Programmable Communication Interface (PCI) data bus network. This network consists of the:

• Integrated Power Module (IPM)  - which incorporates the Power Distribution Center (PDC) and the Front Control Module (FCM) into one assembly.
• Next Generation Controller (NGC)  - which incorporates the Powertrain Control Module (PCM) and the Transmission Control Module (TCM) into one module.
• Instrument Cluster (IC) 
• Electronic Vehicle Information Center (EVIC) 
• Occupant Restraint Controller (ORC) 
• Compass/Mini-Trip Computer (CMTC) 
• Overhead Console 
• Controller Antilock Brake (CAB) 
• Automatic Temperature Control Module (ATC) 
• Power Liftgate Module (PLGM) 
• Audio system 
• Memory/Heated Seat Adjustable Pedal Module 
• Sentry Key Remote Entry Module (SKREEM)  - which performs the functions of the previous two modules - Remote Keyless Entry (RKE) and Sentry Key Immobilizer Module (SKIM).
• Driver Door Module (DDM) and the Passenger Door Module (PDM) 

The BCM provides:

• A battery protection feature. - The BCM will send a message to the IPM to 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.
• Compass/Minitrip support.
• Interior lighting (courtesy/reading lamps).
• Diagnostic reporting.
• Electronic liftgate release (with power door locks).
• Exterior lighting.
• Headlamp time delay (with/without auto headlamps).
• Automatic headlamps (with electrochromatic mirror).
• Illuminated entry.
• A fade to off feature. - This feature dims the interior lighting (courtesy lamps) gradually if the BCM does not receive any new input that would cause the interior lamps to remain on.
• Pulse Width Modulated (PWM) instrument panel dimming.
• Power liftgate switch input. - The BCM has 1 Liftgate switch input located in the overhead console.
• All stalk switch inputs including wipers and light switches.
• Seat belt position input, indicating a buckled or unbuckled seat belt.
• Turn signal operation.
• Fuel Level inputs.
• Monitors rear-door ajar switches, liftgate ajar switches, multi-function switches, multi-function headlight switch, ignition switch, PCI Bus, and diagnostic tool. Based on input from these components, the BCM will send requests over the PCI Bus to have the Instrument Cluster perform various chime operations.

The BCM has internal diagnostic capabilities that assist in diagnosing the vehicle's body system. When an "Open" or a "Short" circuit exists, the DRBIII® scan tool can read the stored BCM Diagnostic Trouble Codes (DTC's). The DTC's are very descriptive in identifying the appropriate feature that has faulted.

Refer to BODY DIAGNOSTIC PROCEDURES for Diagnosis and Testing.