Sent from my radio telephone.
The Canon MF733 is a nice, reliable, economical printer, but it’s really annoying that out of the box it complains about empty toner at 20% levels.
To turn that down or off entirely, go into:
Menu -> Preferences -> Display Settings -> Display Timing for Cart. Prep ON/OFF.
Enter toner level in Custom level and hit apply.
I have a face for radio, and a voice for telegraph.