• Code: 7403
• Description: Developing unit M non-installing error
  No density detection signal is output from toner sensor M in developing unit M.
• Causes: Defective harness between developing unit M and drum relay PWB (YC13), or improper connector insertion. Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Defective toner sensor M. Defective engine PWB.
• Remedy: Defective harness between developing unit M and drum relay PWB (YC13), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective toner sensor M. Replace the developing unit M.
  Defective engine PWB. Replace the engine PWB.

• Code: 7404
• Description: Developing unit Y non-installing error
  No density detection signal is output from toner sensor Y in developing unit Y.
• Causes: Defective harness between developing unit Y and drum relay PWB (YC7), or improper connector insertion. Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Defective toner sensor Y. Defective engine PWB.
• Remedy: Defective harness between developing unit Y and drum relay PWB (YC7), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective toner sensor Y. Replace the developing unit Y.
  Defective engine PWB. Replace the engine PWB.

• Code: 7411
• Description: Drum unit K non-installing error
  The EEPROM of drum PWB K does not communicate normally. Incompatible drum unit K is installed.
• Causes: Defective harness between drum unit K and drum relay PWB (YC2/YC3), or improper connector insertion. Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Installation of incompatible drum unit K. Defective drum PWB K. Defective engine PWB.
• Remedy: Defective harness between drum unit K and drum relay PWB (YC2/YC3), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Installation of incompatible drum unit K. Install drum unit K compatible with the specifications to the printer.
  Defective drum PWB K. Replace the drum unit Y.
  Defective engine PWB. Replace the engine PWB.

• Code: 7412
• Description: Drum unit C non-installing error
  The EEPROM of drum PWB C does not communicate normally. Incompatible drum unit C is installed.
• Causes: Defective harness between drum unit C and drum relay PWB (YC8/YC9), or improper connector insertion. Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Installation of incompatible drum unit C. Defective drum PWB C. Defective engine PWB.
• Remedy: Defective harness between drum unit C and drum relay PWB (YC8/YC9), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Installation of incompatible drum unit C. Install drum unit C compatible with the specifications to the printer.
  Defective drum PWB C. Replace the drum unit C.
  Defective engine PWB. Replace the engine PWB.

• Code: 7413
• Description: Drum unit M non-installing error
  The EEPROM of drum PWB M does not communicate normally. Incompatible drum unit M is installed.
• Causes: Defective harness between drum unit M and drum relay PWB (YC11/ YC12), or improper connector insertion. Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Installation of incompatible drum unit M. Defective drum PWB M. Defective engine PWB.
• Remedy: Defective harness between drum unit M and drum relay PWB (YC11/ YC12), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Installation of incompatible drum unit M. Install drum unit M compatible with the specifications to the printer.
  Defective drum PWB M. Replace the drum unit M.
  Defective engine PWB. Replace the engine PWB.

• Code: 7414
• Description: Drum unit Y non-installing error
  The EEPROM of drum PWB Y does not communicate normally. Incompatible drum unit Y is installed.
• Causes: Defective harness between drum unit Y and drum relay PWB (YC5/YC6), or improper connector insertion. Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Installation of incompatible drum unit Y. Defective drum PWB Y. Defective engine PWB.
• Remedy: Defective harness between drum unit Y and drum relay PWB (YC5/YC6), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective harness between drum relay PWB (YC1) and engine PWB (YC34), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Installation of incompatible drum unit Y. Install drum unit Y compatible with the specifications to the printer.
  Defective drum PWB Y. Replace the drum unit Y.
  Defective engine PWB. Replace the engine PWB.

• Code: 7601
• Description: Left ID sensor error
  The detected signal of left ID sensor is abnormal.
• Causes: Defective harness between left ID sensor and engine PWB (YC5), or improper connector insertiontion. Defective left ID sensor. Defective engine PWB.
• Remedy: Defective harness between left ID sensor and engine PWB (YC5), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective left ID sensor. Replace the left ID sensor.
  Defective engine PWB. Replace the engine PWB.

• Code: 7602
• Description: Right ID sensor error
  The detected signal of right ID sensor is abnormal.
• Causes: Defective harness between right ID sensor and engine PWB (YC6), or improper connector insertion. Defective right ID sensor. Defective engine PWB.
• Remedy: Defective harness between right ID sensor and engine PWB (YC6), or improper connector insertion. Reinsert the connector. Also check for continuity within the connector harness. If none, remedy or replace the harness.
  Defective right ID sensor. Replace the right ID sensor.
  Defective engine PWB. Replace the engine PWB.