Canon BJ-20 User Manual page 23

Notes
You can do the cleaning process without print the check
pattern. To do so, just do step 6 when the printer is online;
this will start the cleaning.
Paper can be fed from the auto sheet feeder as well, See
page 4 on loading paper from the feeder.
The print head cleaning process does not erase any data
sitll remaining in the printer buffer.
The head cleaning can also be executed by turning the
poer switch on while pressing the FWD ADJ and REV ADJ
switches.