Serial Data Reference
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 scan tool communicates over the various busses on the vehicle. When a scan tool is installed on a vehicle, the scan tool will try to communicate with every module that could be optioned into the vehicle. If an option is not installed on the vehicle, the scan tool will display No Comm for that options specific control module. In order to avert misdiagnoses of No Communication with a specific module, refer to Data Link References for a list of modules, the bus they communicate with, and the RPO codes for a specific module.