You can get the messages using cec-client but since that breaks the connection to Kodi until you restart mediacenter it would probably be more useful to tail the log like Grahamh suggested. You could pipe that into grep if it is a too noisy.
Also in Kodi’s CEC settings make sure you tell it is plugged into the amplifier if that is how you have it connected. Not having that setting correct can make it switch wrong.