Canon Service Tools V5103 !!better!! Link

Requires a direct USB connection. It will not work over Wi-Fi or Ethernet Service Mode:

If you have a PIXMA TS3120, TS3320, TR4520, or G7020 , do not use v5103. You need CST v5400 or newer. Using v5103 on these models can permanently lock the EEPROM. canon service tools v5103

With the printer off:

The software provides a wide array of functions, but the most frequently used features include: Requires a direct USB connection