Body Control Module (BCM)

This vehicle is equipped with a computer system capable of performing multiple engine and body control functions. Vehicle components (windows, locks, mirrors, etc.) are controlled directly by their system module. Each system communicates with other systems on an "interconnecting bus" or serial data line. These systems are all part of the vehicle's computer system providing two-way communication between various engine and body control systems.

Some electrical components are directly connected and controlled by their system module. Other systems accomplish this by sharing data information with other systems on the serial data line to execute various vehicle functions. All system data information (sensors, switches, etc.) can be monitored by any system module that completes the computer system.
All systems on the same serial data line use a communication process similar to a telephone system, where enormous amounts of information can be exchanged on a single data wire.

Communications between each system is accomplished by sending a digitally coded message, consisting of specific information a system module must follow. Each system module is assigned its own recognition code (address). So when a message is sent out on the serial data line, only the particular system module that was assigned that recognition code will respond to the message.

The SBM, which is the power mode master, is responsible for sending a power mode message on the serial data line to other systems. When the power mode message is sent, other systems respond to this message by sending their State of Health Code (SOH) code message indicating they are able to communicate information between other systems.

By communicating data information with other systems on the same serial data line, either input information or specific program information within the system's memory. This can provide more accurate and reliable computer system control functions. The Body Control Module (SBM) uses information from other systems in order to execute some functions. Therefore, before further diagnosis, review the general information on how the SBM computer system operates and how each system interacts with the SBM. This will save diagnostic time, avoid future misdiagnosis, and unnecessary parts replacement.