• Code: C4010
• Description: Polygon motor steady-state problem • The polygon motor rotation is not stable for 5 s after the polygon motor rotation has been stabilized.
• Causes: Poor contact in the polygon motor connector terminals. Defective polygon motor. Defective engine board (KP-5061).
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the LSU. Replace the engine board (KP-5061) and check for correct operation.

• Code: C4200
• Description: BD steady-state problem
  • The MIC detects a BD error for 600 ms after the polygon motor rotation has been stabilized.
• Causes: Defective laser diode. Defective polygon motor. Defective main board (KP-5060).
• Remedy: Replace the LSU. Replace the LSU. Replace the main board (KP-5060) and check for correct operation.

• Code: C6000
• Description: Broken fixing heater wire
  • In fixing warm-up, the time to reach 50°C/122 °F exceeds 13.5 s, the time to reach 100°C/212 °F exceeds 10 s, the time to reach the primary stabilization exceeds 10 s or the time to reach the secondary stabilization exceeds 24 s.
• Causes: Poor contact in the thermistor connector terminals. Thermistor installed incorrectly. Thermal cutout triggered. Heater lamp installed incorrectly. Broken heater lamp wire.
• Remedy: Check the connection of connector CN4 on the power supply board (KP-5059) and the continuity across the connector terminals. Repair or replace if necessary. Check and reinstall if necessary. Check for continuity. If none, replace the thermal cutout. Check and reinstall if necessary. Check for continuity. If none, replace the heater lamp.

• Code: C6020
• Description: Abnormally high fixing unit thermistor temperature
  • The fixing temperature exceeds 230°C/446 °F for 40 ms.
• Causes: Shorted thermistor. Broken heater control circuit on the power supply board (KP-5059).
• Remedy: Measure the resistance. If it is 0 Ω, replace the thermistor. Replace the power supply board (KP-5059) and check for correct operation.

• Code: C6050
• Description: Abnormally low fixing unit thermistor temperature
  • The fixing temperature remains below 90°C/194°F for 1 s.
• Causes: Poor contact in the thermistor connector terminals. Broken thermistor wire. Thermistor installed incorrectly. Thermal cutout triggered. Heater lamp installed incorrectly. Broken heater lamp wire.
• Remedy: Check the connection of connector CN4 on the power supply board (KP-5059) and the continuity across the connector terminals. Repair or replace if necessary. Measure the resistance. If it is ‡ ƒ¶, replace the thermistor. Check and reinstall if necessary. Check for continuity. If none, replace the thermal cutout. Check and reinstall if necessary. Check for continuity. If none, replace the heater lamp.

• Code: C6400
• Description: Zero-crossing signal problem
  • The engine board (KP-5061) does not detect the zero-crossing signal for the time specified below. At power-on: 3 s Others: 5 s
• Causes: Poor contact in the connector terminals. Defective power supply board (KP5059). Defective engine board (KP-5061).
• Remedy: Check the connection of connectors YC7 on the engine board (KP-5061) and CN2 on the power supply board (KP-5059), and the continuity across the connector terminals. Repair or replace if necessary. Check if the zero-crossing signal is output from CN2-11 on the power supply board (KP-5059). If not, replace the power supply board (KP-5059). Replace the engine board (KP-5061) if C6400 is detected while CN2-11 on the power supply board (KP-5059) outputs the zero-crossing signal.

• Code: C7800
• Description: Broken external temperature thermistor
  • The input voltage is 0.5 V or less.
• Causes: Poor contact in the operation board connector terminals. Defective external temperature thermistor.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the operation board and check for correct operation.

• Code: C7810
• Description: Short-circuited external temperature thermistor
  • The input voltage is 4.5 V or more.
• Causes: Poor contact in the operation board connector terminals. Defective external temperature thermistor.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the operation board and check for correct operation.