44015503TH  Rev. 1 
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Oki  Data  CONFIDENTIAL
7.  TROUBLESHOOTING PROCEDURE
7.5.2.(16)  Toner cartridge cannot be recognized. (error code 540, 541, 542, 
543) 
(16-1)  Error caused by the consumable items.
Check item Check work
Action to be taken 
at NG
(16-1-1) Consumable items installation condition
ID unit and toner 
cartridge 
Check that the ID unit is installed in the normal 
position. Check that the lock lever of the toner 
cartridge is locked.
Correct the 
installation to 
the normal 
installation 
condition.
(16-2)  Error caused by the toner sensor
Check item Check work
Action to be taken 
at NG
(16-2-1) Toner sensor condition
Toner sensor  Is the receptor of the toner sensor stained?  Wipe off the 
stain from the 
toner sensor.
Toner sensor Confirm that the toner sensor works normally by 
using the SWITCH SCAN function of the self-
diagnostic mode. 
Place a white paper in front of the toner sensor, 
and check if the SCAN state changes or not.
Replace the 
toner sensor 
board, or the PU 
board, or the 
FFC between 
the toner sensor 
board and the 
PU board.
Note!  Toner sensor operation check method using the SWITCH SCAN function of 
the self-diagnostic mode.
(
1)  How to check operation of the toner sensor at the printer side. 
1. Status change of the toner sensor can be checked from the Operator Panel 
using the self-diagnostic mode. First, switch the display to the Operator Panel 
display. For the method of switching the display to the Operator Panel display, 
refer to section 5.3.2.3 Switch Scan Test
2. Remove the ID unit and the toner cartridge (TC) from a printer. There is a 
window inside a  printer opposing the ID side when viewed from the front of a 
printer. The toner sensor is located inside the window. 
3
. Place a white paper 3 mm away from the sensor window. The white paper 
should be placed in the manner of opposing the toner sensor. 
4
. When light is reflected by a white paper so that incident light falls on the toner 
sensor, the Operator Panel display shows "L". When the paper is moved so that 
any light is not reflected by the paper so that the incident light does not reach 
the toner sensor, "H" is displayed on the Operator Panel. 
5
. If the Operator Panel display toggles between "H" <-> "L" as a paper is flipped 
in front of the toner sensor, it indicates that the toner sensor and the related 
system of the printer are working normally.
  Action to be taken at NG
•  Clean surface of the toner sensor to remove the stains due to residual toner 
and paper dust. 
•  Check the connection condition of the FFC cable at the PU main board (PU) 
and at the toner sensor board (PRZ). 
•  P
erform the operation check again. If the situation is not improved and remains 
unchanged, replace the PU main board (PU) or the toner sensor board (PRZ).
(2) 
How to check operation of the toner sensor at the toner cartridge (TC) side
1. To the position where the toner sensor is confirmed to be operating normally 
in the printer itself by the above paragraph (1), install the TC and the ID unit to 
check operations by observing display on the Operator Panel. 
2. If the ID unit works normally, the display on the Operator Panel will toggle 
between "H" <-> "L" in synchronism with movement of the silver reflector plate 
that is located on the side of the ID. 
  Action to be taken at NG
•   Check operation condition of the respective ID motors by using the Motor & 
Clutch Test of the self-diagnostic mode. 
•   Clean surface of the silver reflector plate on the side of ID to remove stains. (Stain 
due to toner or paper dust) 
•
  Replace the TC of different color and the ID unit as a pair. 
  If a satisfactory operation is attained by using the a pair of TC of different color 
and the ID unit, replace the TC or replace the ID unit.