Description & Operation

WARNING: Deactivate air bag system before performing any service operation. See AIR BAG RESTRAINT SYSTEM article. DO NOT apply electrical power to any component on steering column without first deactivating air bag system. Air bag may deploy.

The Body Control Module (BCM) performs the following functions: Retained Accessory Power (RAP), audible warning functions, interior lighting control, automatic power door locking operations, keyless entry functions, PASS-Key(R) II theft deterrent, BRAKE and door/trunk ajar indicator light control, foglight enable control, day/night mode sensing, twilight sentinel control and transaxle shift select function.

BCM communicates with components using class 2 serial data line. Class 2 serial data line is used by various systems to share data information with other systems in order to execute various vehicle functions. Communication between each system is accomplished by sending digitally coded messages, which consist of specific information the system module must follow. Each system module is assigned its own recognition code, so that it can respond to appropriate messages. The BCM can determine state of health of other systems.

Signals that activate the BCM are known as "wake-up" signals. BCM can enter a sleep state when active control or monitoring of systems has stopped or when BCM is idling. BCM monitors its inputs during the sleep state, which allows BCM to switch between sleep and awake states. BCM is asleep when it is not controlling or monitoring the following wake-up inputs: Instrument panel dimmer switch, door lock ajar switch, door lock switch, a keyless entry signal, inadvertent power (battery rundown) protection transition, or ignition is turned to LOCK, OFF, RUN or ACC position. The BCM will enter a sleep state when all of the following conditions exist: No activity on class 2 serial data line, ignition is turned to LOCK or OFF position, no outputs are commanded, no delay timers are actively counting and no wake-up inputs are present.

BCM has 3 main power feeds and one main ground. Power for BCM's logic and internal driver operation is supplied through circuit No. 2340 (Orange wire). Power for door lock system is supplied through circuit No. 1540 (Orange wire). Power for courtesy lights is suppled through circuit No. 240 (Orange wire).