• Code: C6000
• Description: Broken fixing heater wire • The fixing temperature does not increase for 40 s after the fixing heaters have been turned on for warming up. • The fixing temperature remains below 50°C/122°F for 10 s continuously after the fixing heaters have been turned on during stabilization.
• Causes: Poor contact in the fixing unit thermistor connector terminals. Fixing unit thermistor installed incorrectly. Fixing unit thermostat triggered. Fixing heater M and S installed incorrectly. Broken fixing heater M and S wire.
• Remedy: Check the connection of connector CN7 on the junction A PCB and the continuity across the connector terminals. Repair or replace if necessary. Check and reinstall if necessary. Check for continuity. If none, replace the fixing unit thermostat. Check and reinstall if necessary. Check for continuity. If none, replace the fixing heater M and S.

• Code: C6020
• Description: Abnormally high fixing unit thermistor temperature • The fixing temperature exceeds 230C/464F for 10 s. • The fixing unit temperature detection circuit on the engine PCB detects and abnormally high temperature.
• Causes: Shorted fixing unit thermistor. Broken fixing heater control circuit on the power source PCB.
• Remedy: Measure the resistance. If it is 0 Ω, replace the fixing unit thermistor. Replace the power source PCB and check for correct operation.

• Code: C6030
• Description: Broken fixing unit thermistor • The fixing temperature remains at 0C/32F for 30 s continuously when the fixing heater is on.
• Causes: Poor contact in the fixing unit thermistor connector terminals. Broken fixing unit thermistor wire.
• Remedy: Check the connection of connector CN7 on the junction A PCB and the continuity across the connector terminals. Repair or replace if necessary. Measure the resistance. If it is ∞Ω, replace the fixing unit thermistor.

• Code: C6050
• Description: Abnormally low fixing unit thermistor temperature • The fixing temperature remains below 120C/248F for 10 s.
• Causes: Poor contact in the fixing unit thermistor connector terminals. Broken fixing unit thermistor wire. Fixing unit thermistor installed incorrectly. Fixing unit thermostat triggered. Fixing heater M and S installed incorrectly. Broken fixing heater M and S wire.
• Remedy: Check the connection of connector CN7 on the junction A PCB and the continuity across the connector terminals. Repair or replace if necessary. Measure the resistance. If it is ∞Ω, replace the fixing unit thermistor. Check and reinstall if necessary. Check for continuity. If none, replace the fixing unit thermostat. Check and reinstall if necessary. Check for continuity. If none, replace the fixing heater M and S.

• Code: C6400
• Description: Zero-crossing signal problem • The main PCB does not detect the zero-crossing signal (Z CROSS SIG) for the time specified below. At power-on: 3 s Others: 5 s
• Causes: Poor contact in the connector terminals. Defective power source PCB. Defective main PCB.
• Remedy: Check the connection of connectors CN15- 10 on the main PCB and CN2-7 on the power source PCB, and the continuity across the connector terminals. Repair or replace if necessary. Check if the zero-crossing signal is output from CN2-7 on the power source PCB. If not, replace the power source PCB. Replace the main PCB if C6400 is detected while CN2-7 on the power source PCB outputs the zero-crossing signal.

• Code: C7100
• Description: Toner sensor problem • The toner sensor output voltage is outside the range of 0.5 to 4.5 V during copying or in maintenance item U130. • The toner sensor control voltage cannot be set within the range in maintenance item U130.
• Causes: Defective toner sensor. Poor contact in the toner sensor connector terminals. Defective developer.
• Remedy: Replace the toner sensor. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the developer.

• Code: C7300
• Description: Toner hopper problem • Toner level is not detected when toner empty is detected.
• Causes: Defective toner level detection sensor. Poor contact in the toner level detection sensor connector terminals.
• Remedy: Replace the toner level detection sensor. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable.

• Code: C7500
• Description: Broken drum thermistor wire • The drum thermistor input voltage is 4.5 V or more when the front cover is closed.
• Causes: Broken drum thermistor wire. Poor contact in the drum thermistor connector terminals.
• Remedy: Measure the resistance. If it is ∞Ω, replace the drum thermistor. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable.