Body Control System Description and Operation: Communication

The engine control module (ECM) uses GMLAN communication, while all other control modules, including the body control module (BCM), communicate serial data in universal asynchronous receiver and transmitter (UART). The GMLAN communication is more sophisticated than UART and as such, requires a powertrain interface module (PIM) to convert GMLAN into UART. In simple terms, the ECM communicates in a different language than the other control modules and therefore requires the PIM to translate information into the same language as the other control modules.

The PIM is mounted behind the passenger-side shroud lower trim assembly. Specific software has been developed for use with the scan tool to assist with fault-finding vehicle electrical systems, including the various BCM functions and controls. Scan tool connection for BCM serial data communication is via the data link connector (DLC), attached to the lower right-hand trim of the instrument panel (I/P), to the right of the steering column.