Cannot connect to gateway node of CAN bus through OBD2 port

I wanna connect to can bus of my car. I read in the manuals that obd2 is hooked to high speed can bus of something called CCU node and this CCU node acts as gateway between HS and LS canbus. When i connect to obd2 port canbus via MCP2515 and rotate the ignition key i see no activity, no message comes out of obd2. Am i missing something ? Should not some messages be broadcasting through obd2 port? Or i have to send some requests in advance? My goal is to sniff can messages such as radio, lights, windows and etc.