Dell 3115cn Service Manual page 318

Yes
Replace the ADF
SCANNER ASSY.
(Removal 72/Replacement
50)
Version 1 2006.11.21
Possible causative parts: ADF SCANNER ASSY (PL13.8.1)
Yes
Checking the installation
status
Is the printer installed
on a flat steady
surface?
Checking the document
Yes
Does the document
meet the ADF spec ?
Checking the ADF
Is the ADF closed
No
against platen glass
completely ?
Close the ADF.
No
Reinstall the printer.
Chapter 1 Troubleshooting
No
Use the platen mode or
change the paper type