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

• Code: C6050
• Description: Abnormally low fuser unit thermistor temperature The fuser temperature remains below 90C/194F for 1 s.
• Causes: Poor contact in the thermistor connector terminals. Broken fuser thermistor wire. Fuser thermistor installed incorrectly. Fuser thermostat triggered. Fuser heater M or S installed incorrectly. Broken fuser heater M or S wire.
• Remedy: Poor contact in the thermistor connector terminals. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Broken fuser thermistor wire. Measure the resistance. If it is ∞Ω, replace the fuser thermistor. Fuser thermistor installed incorrectly. Check and reinstall if necessary. Fuser thermostat triggered. Check for continuity. If none, replace the fuser thermostat. Fuser heater M or S installed incorrectly. Check and reinstall if necessary. Broken fuser heater M or S wire. Check for continuity. If none, replace the fuser heater M or S.

• Code: C6400
• Description: Zero-crossing signal problem The engine PWB 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 PWB. Defective engine PWB.
• Remedy: Poor contact in the connector terminals. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Defective power supply PWB. Check if the zero-crossing signal is output from YC2-5 on the power supply PWB. If not, replace the power supply PWB. Defective engine PWB. Replace the engine PWB if C6400 is detected while YC2-5 on the power supply PWB outputs the zero-crossing signal.

• Code: C7750
• Description: Drum type mismatch problem A The drum type does not mach with the software.
• Causes: Defective software of the engine PWB. Defective engine PWB.
• Remedy: Defective software of the engine PWB. Rewrite the software of the engine PWB. Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: C7760
• Description: Drum type mismatch problem B The drum type is undefined.
• Causes: Defective software of the engine PWB. Defective engine PWB.
• Remedy: Defective software of the engine PWB. Rewrite the software of the engine PWB. Defective engine PWB. Replace the engine PWB and check for correct operation.

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