Canon S900, S820, S750, S520

Turn off the printer.
Press and hold the RESUME button, then press and hold the POWER button.
While still holding the POWER button, Release the RESUME button, then press and release the RESUME button two more times in succession.
The printer mechanics will move momentarily. You are now in Service mode. Release the Power Button.
Pressing the RESUME key will select a function; for example, pressing RESUME 4 times will select the clear waste ink counter function. The lamp will alternate color with each key press.

1. Service/factory test printout, including ink sensor check
2. EEPROM info printout
3. EEPROM initialization

4. Clear the waste-ink counter
5. Printer model setting. (more selections beyond this- leave this alone)

After selecting mode, press the POWER button to commit the change, and return to the top of the function selection menu. Pressing the POWER button again turns off the printer for a restart.