Chevrolet Equinox Service Manual: Body Control System Description and Operation Body Control Modules

The body control system consists of the body control module(BCM), communications, and various input and outputs. Some inputs,outputs and messages require other modules to interact with theBCM. The BCM also has discrete input and output terminals tocontrol the vehicle's body functions. The BCM is wired to the highspeed GMLAN serial data bus, low speed GMLAN serial data bus andMultiple LIN buses and acts as a gateway between them.

This vehicle body control module (BCM) functions as the powermode master (PMM). The ignition switch is a low current switch withmultiple discrete ignition switch signals to the PMM fordetermining the power mode that will be sent over the serial datacircuits to the other modules that need this information; the PMMwill activate relays and other direct outputs of the PMM as needed.Refer toPower Mode Description and Operationfor a complete descriptionof power mode functions.

The body control module (BCM) in this vehicle functions as agateway or translator. The purpose of the gateway is to translateserial data messages between the GMLAN high speed bus and the GMLANlow speed bus for communication between the various modules. Thegateway will interact with each network according to that network'stransmission protocol.

All communication between the BCM and a scan tool is on thehigh speed GMLAN serial data circuits. A lost communication DTCtypically is set in modules other than the module with acommunication failure.

The various body control module (BCM) input and outputcircuits are illustrated in the corresponding functional areas onthe BCM electrical schematics. Refer to theBody Control System Schematicsfor more detailedinformation.