Body Control System Circuit

This vehicle is equipped with a Body Control Module (BCM). The BCM performs multiple body and engine control functions. The following vehicle systems are directly connected to the BCM:

^ Retained Accessory Power (RAP)
^ Audible warnings
^ Interior lighting
^ Door locks
^ Keyless entry
^ PASS-Key (R) II theft deterrent
^ Trunk Release

This vehicle also has the following systems:
^ Powertrain Control Module (PCM)
^ Electronic Brake Traction Control Module (EBTCM)
^ Instrument Panel Cluster (IPC)

These vehicle systems communicate with each other on an interconnecting bus, known as the Class 2 serial data link.

Some electrical components are directly connected and controlled by their system module. Other systems accomplish this feature by sharing data information with other systems on the Class 2 serial data link in order to execute various vehicle functions. All of the system data information (sensors, switches, etc.) may be monitored by any system module that completes the computer system.

All systems on the Class 2 serial data link use a communication process similar to a telephone system. Large amounts of information may be exchanged on a single data wire.

Communications between each system is accomplished by sending a digitally coded message. The digitally coded message consists of specific information a system module must follow. Each system module is assigned a recognition code (address). When a message is sent out on the Class 2 serial data link, the BCM provides more accurate and reliable computer system control functions. The BCM uses information from other systems in order to execute some functions. Before further diagnosis, review the following general information:
^ The BCM computer system operation
^ The system interactions with the BCM

Review this information in order to gain the following benefits:
^ Save diagnostic time.
^ Avoid misdiagnosis.
^ Prevent unnecessary parts replacement.