WARNING: This page is about a different car, the 2011 Honda CR-V, 2010 Honda CR-V, 2009 Honda CR-V, 2008 Honda CR-V, and 2007 Honda CR-V. However, it is still accessible from the selected car via links, so may be relevant.
The gauge control module acts as a gateway to allow both systems to share information, the gauge control module translates and relays the information from B-CAN to F-CAN and from F-CAN to B-CAN.