• Code: C7404
• Description: Developing unit Y type mismatch problem
  Absence of the developing unit Y is detected.
• Causes: Developing unit connector inserted incorrectly.
  Different type of the developing unit is installed
• Remedy: Developing unit connector inserted incorrectly. Reinsert the developing unit connector if necessary.
  Different type of the developing unit is installed. Install the correct developing unit.

• Code: C7411
• Description: Drum unit K type mismatch problem
  Absence of the drum unit K is detected.
• Causes: Drum unit connector inserted incorrectly.
  Different type of the drum unit is installed.
• Remedy: Drum unit connector inserted incorrectly. Reinsert the drum unit connector if necessary.
  Different type of the drum unit is installed. Install the correct drum unit.

• Code: C7412
• Description: Drum unit C type mismatch problem
  Absence of the drum unit C is detected.
• Causes: Drum unit connector inserted incorrectly.
  Different type of the drum unit is installed.
• Remedy: Drum unit connector inserted incorrectly. Reinsert the drum unit connector if necessary.
  Different type of the drum unit is installed. Install the correct drum unit.

• Code: C7413
• Description: Drum unit M type mismatch problem
  Absence of the drum unit M is detected.
• Causes: Drum unit connector inserted incorrectly.
  Different type of the drum unit is installed.
• Remedy: Drum unit connector inserted incorrectly. Reinsert the drum unit connector if necessary.
  Different type of the drum unit is installed. Install the correct drum unit.

• Code: C7414
• Description: Drum unit Y type mismatch problem
  Absence of the drum unit Y is detected.
• Causes: Drum unit connector inserted incorrectly.
  Different type of the drum unit is installed.
• Remedy: Drum unit connector inserted incorrectly. Reinsert the drum unit connector if necessary.
  Different type of the drum unit is installed. Install the correct drum unit.

• Code: C7420
• Description: Transfer belt unit type mismatch problem
  Absence of the transfer belt unit is detected.
• Causes: Transfer belt unit connector inserted incorrectly.
  Different type of the transfer belt unit is installed.
• Remedy: Transfer belt unit connector inserted incorrectly. Reinsert the transfer belt unit connector if necessary.
  Different type of the transfer belt unit is installed. Install the correct transfer belt unit.

• Code: C7800
• Description: Broken external thermistor wire
  An abnormal value is detected in the input data to the outer temperature sensor.
• Causes: Poor contact in the connector terminals.
  Defective PWB.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC1 on the main front PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective PWB. Replace the main front PWB or engine PWB and check for correct operation.

• Code: C7901
• Description: Drum K EEPROM error
  No response is issued from the device in reading/writing for 5 ms or more and this problem is repeated five times successively. Mismatch of reading data from two locations occurs eight times successively. Mismatch between writing data and reading data occurs eight times successively.
• Causes: Poor contact in the connector terminals.
  Defective drum PWB K.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC3 on the main front PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective drum PWB K. Replace the drum unit K.