• Code: 6400
• Description: Zero-cross signal error
  While fuser heater ON/OFF control is performed, the zero-cross signal is not input within 3 s.
• Causes: Defective PWB.
• Remedy: Defective PWB. Replace the engine PWB or power source PWB and check for correct operation.

• Code: 7000
• Description: Toner motor problem
  The rated speed achievement signal won’t turn to L in 5 s since the motor is activated. The rated speed achievement signal turns to H every other 5 s after the machine is stabilized.
• Causes: Poor contact in the connector terminals. Broken the gear. Defective toner motor M/C/Y/BK. Defective engine PWB.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC30 on the engine PWB and the connector on the toner motor, and the continuity across the connector terminals. Repair or replace if necessary.
  Broken the gear. Check visually and replace the gear if necessary.
  Defective toner motor M/C/Y/BK. Run maintenance item U135 and check if the toner motor operates. If not, replace the toner motor.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7101
• Description: Toner sensor BK problem
  Sensor output value of 78 or less or 944 or more continued for 3 s.
• Causes: Defective developing unit BK. Defective engine PWB.
• Remedy: Defective developing unit BK. Replace the developing unit BK.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7102
• Description: Toner sensor C problem
  Sensor output value of 78 or less or 944 or more continued for 3 s.
• Causes: Defective developing unit C. Defective engine PWB.
• Remedy: Defective developing unit C. Replace the developing unit C.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7103
• Description: Toner sensor M problem
  Sensor output value of 78 or less or 944 or more continued for 3 s.
• Causes: Defective developing unit M. Defective engine PWB.
• Remedy: Defective developing unit M. Replace the developing unit M.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7104
• Description: Toner sensor Y problem
  Sensor output value of 78 or less or 944 or more continued for 3 s.
• Causes: Defective developing unit Y. Defective engine PWB.
• Remedy: Defective developing unit Y. Replace the developing unit Y.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7200
• Description: Broken internal thermistor wire
  An abnormal value is detected in the input data to inner temperature sensor 1.
• Causes: Poor contact in the connector terminals. Defective laser scanner unit. Defective engine PWB.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC16 on the engine PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective laser scanner unit. Replace the laser scanner unit.
  Defective engine PWB. Replace the engine PWB and check for correct operation.

• Code: 7210
• Description: Short-circuited internal thermistor
  An abnormal value is detected in the input data to inner temperature sensor 1.
• Causes: Poor contact in the connector terminals. Defective laser scanner unit. Defective engine PWB.
• Remedy: Poor contact in the connector terminals. Check the connection of connector YC16 on the engine PWB and the continuity across the connector terminals. Repair or replace if necessary.
  Defective laser scanner unit. Replace the laser scanner unit.
  Defective engine PWB. Replace the engine PWB and check for correct operation.