Scan Tool Does Not Communicate with High Speed GMLAN Device: Notes
WARNING: This page is about a different car, the 2007 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications on the high speed GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module detects a bus-off condition, a DTC U0001 will be set. This DTCs can be retrieved as history only.