I had a search through the ArduPilot source code and couldnt find that text anywhere produced by the Pixhawk so my guess is that whatever serial port terminal software you are running on your PC is producing the message.
What operating system are you on and what serial port terminal are you using to receive the Pixhawk data?
EDIT In fact it looks like this is just a startup message produced by MavProxy. I know little about mavproxy. Maybe you need to analyse the mavproxy startup options?
And also how are you connecting to the Pixhawk? I think that the serial data should come via the USB cable. There is no need to connect anything but the USB which provides power and data