Serial Data Gateway

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2013 GMC Savana, 2013 GMC RV Cutaway, 2013 GMC Cutaway, 2013 Chevrolet RV Cutaway, and 2013 Chevrolet Express. However, it is still accessible from the selected car via links, so may be relevant.

The BCM in this vehicle functions as a gateway or translator. The purpose of the gateway is to translate serial data messages between the GMLAN high speed bus and the GMLAN low speed bus for communication between the various modules. The gateway will interact with each network according to that network's transmission protocol.

One example of this necessary communication is the communication between the Engine/Powertrain Control Module (ECM/PCM) which is high speed serial data and Vehicle Theft Deterrent (VTD) Control Module which is low speed serial data. If these modules can not exchange information, the vehicle will not start.

Communication between the BCM and a scan tool can be on the high speed GMLAN network or low speed GMLAN network. If one network is lost, the BCM can still communicate with the scan tool. A lost communication DTC typically is set in modules other than the module with a communication failure.