Lexmark C91x Service Manual page 205

5055-xxx
Also, when the top surface of the paper lowers during printing and
the up sensor is shielded, the tray motor again rotates forward to
raise the paper.
When the down button is pressed, the tray motor reverses to move
the tray down. During the down motion of the tray, as the top surface
of paper passes the paper level sensor, the tray motor stops. The
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Diagnostic aids