Brother MFC Series Service Manual page 246

(3) Change the detecting conditions, and then check that the indication on the LCD
changes according to the sensor states. For example, insert paper through the
Registration sensor, open the Ink cartridge cover or remove the ink cartridges.
(4) Press [Stop] or [X] to stop this operation and return the machine to the initial stage of
the maintenance mode.
Document detection sensor
Registration sensor
Document scanning
position sensor
Head thermistor
High temperature detector in
the complex IC (for Main PCB)
Carriage motor driver temperature detection
Purge cam sensor
Magenta Ink
remaining
sensor
Document scanner sensor
Locations of Sensors
5-24
Black Ink cartridge
detection sensor
Yellow ink cartridge
detection sensor
Cyan Ink cartridge
detection sensor
Magenta Ink cartridge
detection sensor
Black Ink remaining
sensor
Yellow ink remaining
sensor
Cyan ink remaining
sensor
Ink cartridge cover
sensor
Confidential
(5_002L)