Brother MFC4820C Service Manual page 153

(2) Change the detecting conditions (e.g., open the scanner unit or ink slot cover, insert paper
through the registration sensor or paper width sensor, or remove the ink cartridges), and then
check that the indication on the LCD changes according to the sensor states.
(3) To stop this operation and return the equipment to the initial stage of the maintenance mode,
press the Stop/Exit key.
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