If you use a Canon PC940 copier for home or business, replacing the toner cartridge is part of normal maintenance. The best way to tell when the toner needs to be changed is to keep a close eye on the quality of the copies. When the copies begin to get light or exhibit problems with ink coverage, swapping out the empty toner cartridge with a brand new one should resolve those common issues and let you get back to work quickly.
Remove the new toner cartridge from the box. Take off any packaging materials used to protect the Canon toner cartridge during shipment.
Open the top of the PC940, and slide the old toner cartridge out of the machine. Set that toner cartridge aside for recycling.
Shake the new toner cartridge back and forth five or six times to distribute the toner powder evenly inside the cartridge. Pull the tab on the side of the toner cartridge to release the toner.
Insert the new toner cartridge in the PC940. Close the top cover, and make a test copy.