The go-to-sleep command is a diagnostic Master request frame (ID 0x3c) with the first data byte being 0x00. The go-to-sleep command is a broadcast message to all nodes on the bus. It signifies that the Lin bus is shutting down. What the node does then is the application specific. There is no predefined behavior on the LINFlexD module. So no, LINFlexD does not automatically go to sleep.
