• Code: 7411
• Description: Drum unit BK type mismatch problem
  Absence of the drum unit BK 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: 7412
• 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: 7413
• 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: 7414
• Description: Drum unit Y type mismatch proble
  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: 7420
• 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: 7800
• 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 engine PWB.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC13 on the engine PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7810
• Description: Short-circuited external thermistor
  An abnormal value is detected in the input data to the outer temperature sensor.
• Causes: Poor contact in the connector terminals. Defective engine PWB.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC13 on the engine PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7901
• Description: Drum BK EEPROM error
  Reading from or writing to EEPROM cannot be performed.
• Causes: Poor contact in the connector terminals. Defective drum PWB BK.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC18 on the engine PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective drum PWB BK. Replace the drum unit BK.