• Code: C2551
• Description: Abnormally low toner density detected cyan TCR sensor
  When sampling data is determined in TC ratio calculation control, TCR sensor output is higher than a predetermined value for a predetermined number of times in a row even though there is toner in the sub hopper
• Remedy: 1 Perform image troubleshooting procedure if image density is low. 2 Reinstall developing unit. 3 Reinstall toner cartridge. 4 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16 for proper connection and correct as necessary. 5 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 6 M10 operation check M10 PRCB CN14-13 to 16 20-C 7 M6, M7. M8, M9 operation check PRCB CN14-13 to 16 (M6) PRCB CN14-9 to 12 (M7) PRCB CN14-5 to 8 (M8) PRCB CN14-1 to 4 (M9) 19 to 20-C. 8 If the toner empty sensor and its surroundings inside the sub hopper are dirtied with toner, clean them. 9 Replace the developing unit - - 10 Replace FRB. 11 PRCB ICP21, ICP40, ICP41, ICP44, ICP46 conduction check. 12 Replace PRCB.

• Code: C2552
• Description: Abnormally high toner density detected cyan TCR sensor
  The TC ratio of the toner determined by the toner replenishment control is detected to be the predetermined value or over for consecutive times.
• Remedy: 1 Reinstall developing unit. 2 Reinstall toner cartridge. 3 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16, CN10 for proper connection and correct as necessary. 4 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 5 Replace the developing unit. 6 Replace FRB. 7 Replace PRCB.

• Code: C2553
• Description: Abnormally low toner density detected magenta TCR sensor
  When sampling data is determined in TC ratio calculation control, TCR sensor output is higher than a predetermined value for a predetermined number of times in a row even though there is toner in the sub hopper
• Remedy: 1 Perform image troubleshooting procedure if image density is low. 2 Reinstall developing unit. 3 Reinstall toner cartridge. 4 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16 for proper connection and correct as necessary. 5 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 6 M10 operation check M10 PRCB CN14-13 to 16 20-C 7 M6, M7. M8, M9 operation check PRCB CN14-13 to 16 (M6) PRCB CN14-9 to 12 (M7) PRCB CN14-5 to 8 (M8) PRCB CN14-1 to 4 (M9) 19 to 20-C. 8 If the toner empty sensor and its surroundings inside the sub hopper are dirtied with toner, clean them. 9 Replace the developing unit - - 10 Replace FRB. 11 PRCB ICP21, ICP40, ICP41, ICP44, ICP46 conduction check. 12 Replace PRCB.

• Code: C2554
• Description: Abnormally high toner density detected magenta TCR sensor
  The TC ratio of the toner determined by the toner replenishment control is detected to be the predetermined value or over for consecutive times.
• Remedy: 1 Reinstall developing unit. 2 Reinstall toner cartridge. 3 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16, CN10 for proper connection and correct as necessary. 4 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 5 Replace the developing unit. 6 Replace FRB. 7 Replace PRCB.

• Code: C2555
• Description: Abnormally low toner density detected yellow TCR sensor
  When sampling data is determined in TC ratio calculation control, TCR sensor output is higher than a predetermined value for a predetermined number of times in a row even though there is toner in the sub hopper
• Remedy: 1 Perform image troubleshooting procedure if image density is low. 2 Reinstall developing unit. 3 Reinstall toner cartridge. 4 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16 for proper connection and correct as necessary. 5 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 6 M10 operation check M10 PRCB CN14-13 to 16 20-C 7 M6, M7. M8, M9 operation check PRCB CN14-13 to 16 (M6) PRCB CN14-9 to 12 (M7) PRCB CN14-5 to 8 (M8) PRCB CN14-1 to 4 (M9) 19 to 20-C. 8 If the toner empty sensor and its surroundings inside the sub hopper are dirtied with toner, clean them. 9 Replace the developing unit - - 10 Replace FRB. 11 PRCB ICP21, ICP40, ICP41, ICP44, ICP46 conduction check. 12 Replace PRCB.

• Code: C2556
• Description: Abnormally high toner density detected yellow TCR sensor
  The TC ratio of the toner determined by the toner replenishment control is detected to be the predetermined value or over for consecutive times.
• Remedy: 1 Reinstall developing unit. 2 Reinstall toner cartridge. 3 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16, CN10 for proper connection and correct as necessary. 4 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 5 Replace the developing unit. 6 Replace FRB. 7 Replace PRCB.

• Code: C2557
• Description: Abnormally low toner density detected black TCR sensor
  When sampling data is determined in TC ratio calculation control, TCR sensor output is higher than a predetermined value for a predetermined number of times in a row even though there is toner in the sub hopper
• Remedy: 1 Perform image troubleshooting procedure if image density is low. 2 Reinstall developing unit. 3 Reinstall toner cartridge. 4 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16 for proper connection and correct as necessary. 5 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 6 M10 operation check M10 PRCB CN14-13 to 16 20-C 7 M6, M7. M8, M9 operation check PRCB CN14-13 to 16 (M6) PRCB CN14-9 to 12 (M7) PRCB CN14-5 to 8 (M8) PRCB CN14-1 to 4 (M9) 19 to 20-C. 8 If the toner empty sensor and its surroundings inside the sub hopper are dirtied with toner, clean them. 9 Replace the developing unit - - 10 Replace FRB. 11 PRCB ICP21, ICP40, ICP41, ICP44, ICP46 conduction check. 12 Replace PRCB.

• Code: C2558
• Description: Abnormally high toner density detected black TCR sensor
  The TC ratio of the toner determined by the toner replenishment control is detected to be the predetermined value or over for consecutive times.
• Remedy: 1 Reinstall developing unit. 2 Reinstall toner cartridge. 3 Check the connector between developing unit-FRB CN13, CN14, CN15, CN16, CN10 for proper connection and correct as necessary. 4 Check the connector between FRB CN1, CN3-PRCB CN7, CN9 for proper connection and correct as necessary. 5 Replace the developing unit. 6 Replace FRB. 7 Replace PRCB.