It is ink low error U051
Disconnect the power cable
2. Connect it while holding down the power button
3. With the power button still down, press twice the "Cancel/Stop" red button
4. Release the power button
5. The prints turns into a kind of factory mode...(wait for about 10 seconds, utile it says "Idle")
6. Press the ">" (next to the "OK" button) once.” Shipping Mode 3"
7. Press the "OK" button.
8. Press "OK" again for "Without cleaning"
9. A test page will print.
10. Open the cover, like you are about to change the cartridges.
11. Disconnect the power cable again.
12. Take out both cartridges.
13. Close the cover.
14. Connect the power cable once again.
15. Turn the printer on.
16. Now just put the cartridges back...
Or try this
Here the Solution to reset the ink level for Canon Pixma MX300 follow this steps to reset the ink level in your canon MX300.
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- Switch off the Canon MX300 and disconnect the power cable.
- While press and hold the power button, Connect the power cable to electric socket.
- While pressing the power button, press the “Cancel/Stop” button (red button).
- Now release the power button and the printer turns into a kind of factory mode. Wait for 10 seconds until it says “idle”.
- Press “>” (next button) once “Shipping Mode 3′ then Press the “OK” button. Press “OK” again for “without cleaning”.
- A test page will print.
- Open the cover, like you are about to change the cartridges.
- Disconnect the power cable again without switch off the printer.
- Take out the both cartridges.
- Close the cover.
- Connect the power cable and turn on the printer.
- Now just put the cartridges back and the ink level in the canon Pixma MX300 have full again.
All The Best: Pineworks