Canon 3170 Series - Manual (Page 381)

15-30 Maintenance & Frequently Asked Questions Chapter 15
LASER CLASS 3170 Series.
CFYA/YAH/YAN 120v US V1.0
5. Gently close the upper unit of the ADF cover until you hear it
lock.
MAKE SURE THAT THE UPPER UNIT OF THE ADF COVER IS
LOCKED IN POSITION SECURELY BEFORE PROCEEDING TO
STEP 6.
6. Lift the document feeder tray, and gently open the ADF cover
until it stops, grasping the document feeder tray and the ADF
cover at the same time.