How to reset waste ink pad on Canon Pixma MP520

How to reset waste ink pad on Canon Pixma MP520
Solution for error code 5B00:

1. Switch the printer OFF
2. Press buttons 1 + 2 + 3 and 4 (simultaneously using four fingers). See picture bellow
3. Keep pressing this four buttons for 10 seconds
4. Release the On/Off button (number 4) (Keeping pressing the others)
5. After a few seconds (when the printer go ON) you can release buttons 1, 2, 3