Toner sensor error on an Oki C3520 Laser

Needs Black Toner and Yellow Drum
Replace both while printer is on

I would uninstall and reinstall the driver:

http://my.okidata.com/oki-faq.nsf/FAQCentral/77AE0D0F5AEA7EDD85257666004F56C7?OpenDocument

The plastic shutter in the ID is fully or partially covering the toner sensor window.

Move the cover upward to allow for the sensor to become fully exposed prior to reinstalling the drum.

look this solution http://my.okidata.com/oki-faq.nsf/FAQCentral/C384D8F74A91CF6E8525765E0065F636?OpenDocument
here the solution for your problem
i hope that it's helpful .... bye

Replace Y toner cartridge (use oki ones or risk it not working for you, but I have warned you now) it was low (sensor clicking) now it is empty(stop operations)

Chances are that you will then need the other colours too, they all go about same time, but depends on what colours you print, normally black goes first then 3 colours, lights and software should indicate but once it is empty totally all will stop...

You can check visually by removing suspect drum and toner, putting on desk, remove toner cart. from top of drum, inside drum running the width of top surface is a 2 x 15cm wide slot, it needs to have the toner to the brim of this slot (foam edged), there also needs to be toner left in the toner unit itself thats sits on top of this slot.

Cheers

pls try to upgrade the firmware carefully

THE TONER CONTAIN NEED TO BE WASHED OUT WITH SPECAL CHEMICALS, PRINTS NEED MAINTNANCE, OVER FLOW CONTAINER MAY HAVE TO BE EMPTYED ALL SO, CORRORNA WIRES NEED TO BE CLEANED
DRUM MAY MAY NEED SERVICE ALSO

ROD

yes u can use it with black and white 

The toner cartridge has a small window from outside where the dark blue handle. You should turn a photodrum gear wheel while the window will not open. After that insert a drum unit and work.
If you have "start cartridge" that doesnt work....

When installing the C3300 printer, or when replacing the toner cartridge, be sure to fully insert the toner cartridge into the image drum, and make sure the blue lever is pushed ALL THE WAY toward the back of the printer (fully locked position). If it is not fully closed (locked), a "toner sensor" or "toner empty" message may result.