The message TONER LOW or INK LOW appears on the printer display or computer monitor when one of the toner or ink cartridges is estimated to be running low, but the cartridge has not probably not reached the end of it's life. This is an alert the toner or ink cartridge will reach its end of life in the near future. It's always a good idea to have a back up cartridge ready to replace since many printers will lock you out from printing when an empty message appears.
