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How do I find and resolve Toner Sensor Errors?


If your printer displays a toner sensor error please check the following...


Please carry out the following instructions if you receive one of the following error codes:

540 Toner Sensor Error, Colour: Yellow
541 Toner Sensor Error, Colour: Magenta
542 Toner Sensor Error, Colour: Cyan
543 Toner Sensor Error, Colour: Black

The printer contains four image drums; cyan, magenta, yellow and black.

How do I find the Toner Sensors?

Press the cover release and open the top cover fully and note the positions of the four cartridges:

Toner Position


Make sure the toner cartridge is correctly positioned and the right hand clip is pushed back

Toner cartridge.png

Lift the image drum (complete with the toner cartridge) up and out of the printer

Lift the image drum.png

On the right hand side of the toner there is a sensor patch; make sure this is clean.

Depending on the age of your consumable the patch will look like either Image 1 or Image 2.

Consumable patch.png       

              Image 1                                                                            Image 2

If the patch is dirty it can be cleaned with a soft lint free cloth.

Now look inside the printer - opposite to where the sensor patch would sit. 
There is a black square with a sensor located inside, make sure this is clean - see Image 3


                        Image 3

Replace the drum and toner and close the printer cover

If you still have an error message please contact your local OKI Printing Solutions office for further assistance.


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