TROUBLESHOOTING GUIDE 
SM 4-21 G104 
Trouble-
shooting 
4.3 TROUBLESHOOTING GUIDE 
NOTE: When replacing the engine control board, remove the NVRAM from the 
original engine control board and install it on the new one. 
SYMPTOM 
4.3.1 BLANK PRINT 
Symptom  Possible cause  Necessary actions 
Defective LDU  Replace the LDU. 
Defective PCU  Replace the PCU. 
Defective transfer belt unit 
Replace the transfer belt 
unit. 
Incorrect action of transfer 
roller 
Check the guide and the 
transfer roller. 
Defective high voltage 
supply board 
Replace high voltage supply 
board 1 or 2. 
No image is printed. 
Defective engine board 
(EGB) 
Replace the engine board 
(EGB). 
 
4.3.2 ALL-BLACK PRINT 
Symptom  Possible cause  Necessary actions 
Incorrectly installed PCU  Install the PCU correctly. 
Defective PCU  Replace the PCU. 
Defective high voltage supply 
board 
Replace high voltage supply 
board 1 or 2. 
Defective LDU  Replace the LDU. 
Defective engine board 
(EGB) 
Replace the engine board 
(EGB). 
All the paper is black. 
Defective main board  Replace the main board.