• Code: 4000
• Description: Polygon motor synchronization problem
  • When the polygon motor starts, the motor does not become stable even after 20 s.
• Causes: Poor contact in the polygon motor connector terminals. Defective polygon motor. Defective power supply unit. Defective power supply from engine controller PWB. Defective engine controller PWB.
• 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 YC2-1 on the engine controller PWB. If not, replace the power supply unit. Check if 24 V DC is output from YC8-10 on the engine controller PWB. If not, replace the engine controller PWB. Replace the engine controller PWB.

• Code: 4010
• Description: Polygon motor steady-state problem
  • When high-speed rotation from lowspeed rotation is requested, the motor does not become stable even after 20 s.
• Causes: Poor contact in the polygon motor connector terminals. Defective polygon motor. Defective power supply unit. Defective power supply from engine controller PWB. Defective engine controller PWB.
• 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 YC2-1 on the engine controller PWB. If not, replace the power supply unit. Check if 24 V DC is output from YC8-10 on the engine controller PWB. If not, replace the engine controller PWB. Replace the engine controller PWB.

• Code: 4200
• Description: BD steady-state problem
  • While the polygon motor is on, a BD error is detected three times continuously at 200 ms intervals.
• Causes: Defective laser diode. Defective polygon motor. Defective engine controller PWB.
• Remedy: Replace the LSU. Replace the LSU. Replace the engine controller PWB and check for correct operation.

• Code: 5300
• Description: Broken cleaning lamp wire
  While the cleaning lamp is on, the broken cleaning lamp wire detection signal is detected for 2 s continuously.
• Causes: Defective cleaning lamp. Defective engine controller PWB.
• Remedy: Replace the cleaning lamp. Replace the engine controller PWB and check for correct operation.

• Code: 6000
• Description: Broken fuser heater wire
  • When the power is turned on or at the start of fuser unit control from the sleep mode, 10 s after fuser heater M is turned on, the detected temperature of fuser unit thermistor 2 is lower than 40 °C/104 °F.
• Causes: Poor contact in the fuser unit thermistor 1 or 2 connector terminals. Fuser unit thermistor 1 or 2 installed incorrectly. Fuser unit thermostat triggered. Fuser heater M or S installed incorrectly. Broken fuser heater M or S wire.
• Remedy: Check the connection of connector YC10 on the engine controller PWB and the continuity across the connector terminals. Repair or replace if necessary. Check and reinstall if necessary. Check for continuity. If none, replace the fuser unit thermostat. Check and reinstall if necessary. Check for continuity. If none, replace the fuser heater M or S.

• Code: 6020
• Description: Abnormally high fuser unit thermistor temperature
  • Fuser unit thermistor 1 detects temperature 250 °C/482 °F or higher. • Fuser unit thermistor 2 detects temperature 220 °C/428 °F or higher.
• Causes: Shorted fuser unit thermistor 1 or 2. Broken fuser unit heater control circuit on the power supply unit.
• Remedy: Measure the resistance. If it is 0 Ω, replace the fuser unit thermistor 1 or 2. Replace the power supply unit.

• Code: 6050
• Description: Abnormally low fuser unit thermistor temperature
  • When only fuser heater M is on, fuser unit thermistor 2 detects temperature lower than 80 °C/176 °F during printing. • When fuser heater M and fuser unit heater S are on, fuser unit thermistor 2 detects temperature lower than 80 °C/176 °F or fuser unit thermistor 1 detects temperature lower than 100 °C/212 °F during ptinting.
• Causes: Poor contact in the fuser unit thermistor 1 or 2 connector terminals. Broken fuser unit thermistor 1 or 2 wire. Fuser unit thermistor 1 or 2 installed incorrectly. Fuser unit thermostat triggered. Fuser heater M or S installed incorrectly. Broken fuser heater M or S wire.
• Remedy: Check the connection of connector YC10 on the engine controller PWB and the continuity across the connector terminals. Repair or replace if necessary. Measure the resistance. If it is ∞, replace the fuser unit thermistor 1 or 2. Check and reinstall if necessary. Check for continuity. If none, replace the fuser unit thermostat. Check and reinstall if necessary. Check for continuity. If none, replace the fuser heater M or S.

• Code: 6400
• Description: Zero-crossing signal problem
  • The engine controller PWB does not detect the zero-crossing signal (Z CROSS SIG) for the time specified below. At power-on: 5 s Others: 5 s
• Causes: Poor contact in the connector terminals. Defective power supply unit. Defective engine controller PWB.
• Remedy: Check the connection of connectors YC1-3 on the engine controller PWB and YC2-6 on the power supply unit, and the continuity across the connector terminals. Repair or replace if necessary. Check if the zero-crossing signal is output from YC2-6 on the power supply unit. If not, replace the power supply unit. Replace the engine controller PWB if C6400 is detected while YC2-6 on the power supply unit outputs the zero-crossing signal.