Very late production iR2016 units (after 2008) support USB firmware recovery. This is not documented in early manuals but verified in field:
Canon ImageCLASS MF6590: Resolving 'Downloading Standby' Issue canon ir2016 download standby error verified
A firmware update was interrupted (power loss or cable unplugged). Very late production iR2016 units (after 2008) support
Wait at least 5–10 minutes to ensure all residual charge is gone. Plug it back in and restart. 2. Clear All Settings (Maintenance Mode) canon ir2016 download standby error verified
Technicians use a specific piece of software called the Canon Service Support Tool (often version 3.22E or newer for this era of machine).