• Code: C4000
• Description: Polygon motor synchronization problem • The polygon motor does not reach the stable speed within 9 s of the START signal turning on.
• Causes: Poor contact in the polygon motor connector terminals. Defective polygon motor. Defective power source PCB. Defective engine PCB.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the LSU. Check if 24 V DC is supplied to CN1-4 on the main PCB. If not, replace the power source PCB. Check if 24 V DC is output from CN14-14 on the engine PCB. If not, replace the main PCB.

• Code: C4010
• Description: Polygon motor steady-state problem • The polygon motor rotation is not stable for 600 ms after the polygon motor rotation has been stabilized.
• Causes: Poor contact in the polygon motor connector terminals. Defective polygon motor. Defective power source PCB. Defective engine PCB.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the LSU. Check if 24 V DC is supplied to CN1-4 on the main PCB. If not, replace the power source PCB. Check if 24 V DC is output from CN14-14 on the engine PCB. If not, replace the main PCB.

• Code: C4200
• Description: BD steady-state problem • The VTC detects a BD error for 600 ms after the polygon motor rotation has been stabilized.
• Causes: Defective laser diode. Defective polygon motor. Defective main PCB.
• Remedy: Replace the LSU. Replace the LSU. Replace the main PCB and check for correct operation.

• Code: C5100
• Description: Main charger problem MC ALM signal is detected continuously for 400 ms when MC REM signal is turned on.
• Causes: Leakage during main charging. Defective high voltage transformer PCB.
• Remedy: Check and clean the main charger unit. Replace the high voltage transformer PCB and check for correct operation.

• Code: C5110
• Description: Transfer/separation charger problem SC/TC ALM signal is detected continuously for 400 ms when SC/TC REM signal is turned on.
• Causes: Leakage during transfer/separation charging. Defective high voltage transformer PCB.
• Remedy: Check and clean the transfer charger unit. Replace the high voltage transformer PCB and check for correct operation.

• Code: C5500
• Description: Drum surface potential sensor problem 1 Drum surface potential sensor output voltage is 0.5 V or less when MC REM signal is turn on. (except during stepping control)
• Causes: Poor contact in the drum surface potential sensor connector terminals. Defective drum surface potential sensor. Defective engine PCB. Defective high voltage transformer PCB.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, repair or replace the cable. Replace the drum surface potential sensor. Replace the engine PCB and check for correct operation. Replace the high voltage transformer PCB and check for correct operation.

• Code: C5510
• Description: Drum surface potential sensor problem 2 Drum surface potential sensor output voltage is 4.5 V or less when MC REM signal is turn on. (except during stepping control)
• Causes: Defective drum surface potential sensor.
• Remedy: Replace the drum surface potential sensor.

• Code: C5600
• Description: Drum surface potential problem 1 • Maximizing the grid output cannot set the potential.
• Causes: Deteriorated main charger. Grid or main charger shield is dirty. Defective high voltage transformer PCB. Defective engine PCB.
• Remedy: Check the main charger wire and replace it if necessary. Clean the grid or main charger shield if necessary. Replace the high voltage transformer PCB and check for correct operation. Replace the engine PCB and check for correct operation.