Body Control Module: Description

WARNING: Vehicle is equipped with air bag supplemental restraint system. Before attempting ANY repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEM article.

The Body Control Module (BCM) communicates with various systems over the serial data line in order to control the following functions: Bulb over voltage protection; door, hatch and hood ajar status; exterior and interior lighting control; hatch release control; heated mirror control; horn relay; key-in-ignition status; load shed control; monitored loads control; PASS-Key(R) system; power mode master; rear defogger control; steering column lock/unlock control; Traction Control System (TCS) activation control; Universal Theft Deterrent (UTD); and vehicle configuration (RPO codes).

Some vehicle systems share data over a serial data line 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 acts as the power mode master, which can determine state of health of other systems.

Signals that activate the BCM are known as "wake-up" signals. BCM is asleep when it is not controlling or monitoring the following wake-up functions: Any activity on serial data line; hatch or door ajar switch; hatch release switch; key-in-ignition switch; monitored load relay; any exterior light function; battery disconnection and reconnection; or ignition is turned on. The BCM will enter a sleep state when all of the following conditions exist: No activity on serial data line, ignition is turned off, no outputs are commanded, no delay timers are actively counting and no wake-up inputs are present.