• Code: 7402
• Description: Developing unit C type mismatch problem
  Absence of the developing unit C is detected.
• Causes: Developing unit connector inserted incorrectly.
  Different type of the developing unit is installed.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• Code: 7403
• Description: Developing unit M type mismatch problem
  Absence of the developing unit M is detected.
• Causes: Developing unit connector inserted incorrectly.
  Different type of the developing unit is installed.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• Code: 7404
• 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.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• Code: 7411
• 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.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• 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.
  Defective PWB
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• 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.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• Code: 7414
• 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.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.

• 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.
  Defective PWB.
• 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.
  Defective PWB. Replace the engine PWB check for correct operation.