Brother DCP-L8400CDN Service Manual page 256

(4) Pass the Second side CIS flat cable through the ADF unit.
Note:
Remove the Upper ADF chute from the ADF unit in advance.
(Refer to "9.28 ADF Cover/Document Detection Sensor PCB ASSY/ First Side Docu-
ment Scanning Position Sensor PCB ASSY/Second Side Document Scanning Position
Sensor PCB ASSY (Duplex Scanning Model Only)" in this chapter.)
Second side CIS flat cable
Upper ADF chute
(5) Affix double-sided adhesive tape to the Flat cable holder as shown in the figure below.
(If the double-sided adhesive tape has already been affixed, be sure to remove it, and
then affix new double-sided adhesive tape.)
Fig. 3-106
Flat cable holder
Fig. 3-107
3-92
Lower ADF chute
Double-sided adhesive tape
Confidential