Reset MP390 Waste Ink Full Tank 
The below reset procedure worked for me. I did not have to clean the waste-ink sponge. Many thanks to lp who originally posted it and to "Anonymous" who reposted it.
1)Printer on, press Additional Functions, Scan, Copy, Scan
Now you should be in service mode from there for waste ink tank reset
2)Select Test mode which is like the last avalabe selection
3)Select #8 Printer Test, it will do something here like cleaning or something then it will come up with some other option this is where it gets a bit confusing cause now all it says is like 8-2 or 8-3 push the + or - button until it says 8-3 then hit the select button
The menu will now say
EEPRON Clear
Select Ink count which is option (0) and press set
Then press Stop/Reset Followed by the power button and then wait for it to restart.
Linear Mode
