Basically service mode is used to reset the printer. Thus to active service mode do as follow:
- Turn on your printer.
- Hold the reset button on printer.
- During pressing reset button, hold color start button for 5 sec.
- Release both buttons.
- Press and hold the “Tool” button.
- While pressing on the “Tool” button, press and hold the “Reset button“.
- Now release both tool button and reset button.
Now your printer is successfully comes under service mode. You can check details in Cnaon Pixma MX397 Manual- www.guideusermanual.com/product-name-pixma-mx397-manual&po=208778&lang=English for better understanding.