Error Code C2355 is a Transfer Belt Cleaner Cooling Fan Motor Failure to Turn on Konica Minolta bizhub colour machines. It fires when the fan lock signal from the transfer belt cleaner cooling fan remains HIGH for a predetermined continuous period while the fan is commanded to run — meaning the control board is telling the fan to spin, but the lock signal feedback confirms the fan blades are not rotating.

The transfer belt cleaner cooling fan is a dedicated fan that removes heat and toner dust from the area around the transfer belt cleaning unit. Without it, heat builds up around the cleaner, affecting cleaning blade performance, toner collection efficiency, and ultimately image quality. The machine stops when C2355 fires to protect these components from thermal damage.

All Affected Models and Exact Component References

C2355 maps to different fan designations, connector paths, ICP locations, and control boards depending on the bizhub generation. Always confirm your model and use the correct row before starting any diagnosis.

What Does Error Code C2355 Mean?

Like every cooling fan in the bizhub machine, the transfer belt cleaner fan (FM2/FM6/FM5/FM11) has a built-in lock signal — a feedback mechanism generated by a Hall-effect sensor or encoder inside the fan motor. When the fan blades rotate, this signal pulses continuously. When the fan is stalled or stopped, the signal stays in a fixed HIGH state.

The control board monitors this lock signal in real time and compares it against its fan drive commands. C2355 fires when the board commands the fan to run and the lock signal remains HIGH beyond the allowed threshold period — indicating the blades are not rotating despite the drive command being sent.

The failure can be genuine (blades physically stopped) or apparent (blades turning but the internal feedback sensor has failed). The service mode operation check distinguishes between these two cases and directs you to the correct fix without unnecessary parts replacement.

The transfer belt cleaner cooling fan serves a specific and important purpose. The transfer belt cleaning unit — which removes residual toner from the belt surface after each print cycle — generates friction heat and toner dust during operation. Without this dedicated cooling fan, the area around the cleaner overheats, causing the cleaning blade to lose elasticity, the collected toner to clump inside the waste toner path, and ultimately leading to image quality defects such as background fogging and streaking. The machine stops at C2355 to prevent this progression.

Common Causes of Error Code C2355

• Fan blades obstructed by accumulated toner or paper dust — the most common cause on older, high-volume machines. Toner and paper dust accumulate on the fan blades over time, increasing rotational mass and drag. Eventually the fan can no longer overcome this resistance and stalls under the combined weight of the debris and the aerodynamic load. The lock signal stays HIGH and C2355 fires. A visible layer of dust or toner on the blades is the clearest diagnostic indicator
• Foreign object lodged in the fan housing — a piece of torn paper, a fragment of packing material from a consumable, or other debris has been sucked into the fan housing and is physically preventing the blades from rotating. Very common after a toner spill near the transfer belt cleaner area or after removing and reinstalling the transfer belt unit without covering the fan intake
• Worn fan motor bearings causing seizure — the fan motor’s bearings have worn out or corroded, causing the rotor to seize or produce high rotational resistance. A fan in this condition may still hum when powered but will not rotate. Common on machines in humid environments or machines that have been idle for extended periods where bearing corrosion can accelerate
• Loose or disconnected connector on FM2/FM6 harness — the fan receives no power or the lock signal line is broken at a connector. Very common after a PM visit, transfer belt unit replacement, or any service where the harness area was disturbed. On the C220/C280/C360, the two-relay path (CN127→CN126→PRCB CN3) means there are three potential connection points to check rather than one
• Blown ICP on the PRCB — an inline circuit protector on the PRCB in the fan power supply path has blown due to a previous overcurrent event (typically from a seized fan motor). The fan connector may be perfect but the fan receives no power. Confirmed when the service mode operation check shows no drive signal at the fan connector even with the check commanded ON. Specific ICPs: PRCB ICP2 on C220/C280/C360; PRCB ICP3 on C224/C284/C364 family; PRCB ICP7 on C452/C552/C652
• Failed fan motor (internal Hall-effect sensor failure) — the fan blades may be physically spinning but the internal feedback sensor has failed, producing a permanent HIGH lock signal regardless of actual fan state. Less common than mechanical causes but confirmed when the fan is visibly spinning during the operation check but C2355 still fires
• Faulty PRCB or MFPB — the control board’s fan drive output circuit or lock signal input circuit has failed — last resort after all physical and connector causes are confirmed and ruled out

Step-by-Step Troubleshooting Procedure

Step 1 — Power Cycle and Listen During Startup

Before any physical inspection, perform a full power cycle and pay attention to the machine during warm-up. This diagnostic step costs nothing and provides immediate useful information.

1. Power the machine fully OFF using the main power switch
2. Disconnect the power cord from the wall outlet and wait 30 seconds
3. Reconnect the power cord and power ON
4. During the startup sequence, listen carefully near the transfer belt cleaner area — the FM2/FM6 fan should be audible during warm-up as a consistent airflow sound
5. If you can hear the fan but C2355 still fires — the fan blades are spinning but the lock signal feedback sensor has failed internally. The fan needs replacement but the bearings and motor coil are fine
6. If you cannot hear the fan at all — the fan is genuinely not spinning. Proceed to physical inspection
7. If C2355 clears and does not return on subsequent startups — the event was transient (a brief startup timing issue). Monitor the machine over the next few print cycles. If C2355 returns, proceed to Step 2

Step 2 — Physically Inspect the Fan Blades and Housing

This step resolves the majority of C2355 cases on high-volume machines and takes under five minutes.

1. Power OFF and unplug the machine
2. Locate the transfer belt cleaner cooling fan (FM2 on most models, FM6 on C220/C280/C360) — it is positioned near the transfer belt cleaner unit, typically accessible from the rear or right-side cover depending on the model. Refer to your service manual for the exact location
3. Visually inspect the fan blades:
   • Look for a thick layer of accumulated toner dust or paper dust on the blade surfaces and around the fan housing — even a modest buildup can significantly increase rotational resistance
   • Look for any foreign object — paper fragment, packing material, toner cartridge chip, staple — caught between the blades or in the fan housing frame
   • Check the fan intake and exhaust paths for obstructions — a blocked intake reduces airflow and causes the motor to work harder, accelerating bearing wear
4. Clean the fan blades:
   • Use a can of compressed air to blow dust from between the blades — hold the blades stationary while blowing to prevent the fan from spinning as a generator, which can create a back-EMF that could damage the motor drive circuit on some boards
   • Use a soft brush to dislodge compacted toner from blade surfaces and housing corners
   • Vacuum or wipe away loosened debris
5. Remove any foreign object found in the housing carefully with tweezers — avoid scratching the blade surfaces or bending the blades, as blade deformation causes vibration and bearing stress
6. After cleaning, manually spin the fan blades by hand — they should rotate freely and smoothly with almost no resistance. Any stiffness, grinding, irregular resistance, or a blade that will not rotate at all indicates bearing wear or seizure. Proceed to Step 3 if the fan is stiff or cannot spin freely after cleaning
7. If the blades are clean and spin freely, power on and test — if C2355 clears, the obstruction was the cause

Step 3 — Inspect and Reseat the Fan Harness Connector

Use the model-specific connector references from the table above to reseat the correct connectors for your machine.

For bizhub C224 / C284 / C364 / C224e / C284e / C364e / C454 / C554 / C7822 / C7828:

1. Power OFF and unplug the machine
2. Trace the FM2 harness from the fan to relay CN115, then from relay CN115 to PRCB CN13
3. Disconnect and firmly reseat the connector at FM2 → relay CN115 — push until it clicks
4. Disconnect and firmly reseat the connector at relay CN115 → PRCB CN13
5. Inspect all pins at both connectors: look for bent pins, toner contamination, green or white oxidation, and harness wire damage at the connector entry points
6. Clean oxidized pins with electrical contact cleaner on a cotton swab — allow to dry completely before reconnecting

For bizhub C220 / C280 / C360:

1. Power OFF and unplug the machine
2. Trace the FM6 harness — it passes through TWO relay connectors before reaching PRCB CN3
3. Reseat connector at: FM6 → relay CN127
4. Reseat connector at: relay CN127 → relay CN126 — this intermediate relay-to-relay connection is the most commonly missed connector on this model family
5. Reseat connector at: relay CN126 → PRCB CN3
6. Inspect all pins at all three connection points

For bizhub C227 / C287 / C367 / C258 / C308 / C368 / C458 / C558 / C658 / 458e / 558e / 658e:

1. Power OFF and unplug the machine
2. Reseat FM2 → relay connector and relay → MFPB connector
3. Inspect all pins for damage and oxidation

For bizhub C452 / C552 / C652 / C654 / C754:

1. Power OFF and unplug the machine
2. Reseat FM5 (or FM11) connector at the PRCB
3. Inspect connector pins carefully

After reseating all connectors, power on and test. If C2355 clears, monitor the machine — if the error returns within days or weeks, the connector housing is degraded and should be replaced rather than reseated repeatedly.

Step 4 — Perform the Fan Motor Operation Check in Service Mode

The service mode operation check is the definitive test before replacing any component. It tells you in seconds whether the fan is receiving a drive signal but not responding (fan failure) or whether the drive signal is absent (ICP or board failure).

For bizhub C224 / C284 / C364 family:

1. Enter Service Mode (refer to your model’s service manual for the access procedure)
2. Navigate to the fan load check / I/O check section
3. Command FM2 to run — monitor:
   • PRCB CN13-8 (REM) — the drive command signal sent to the fan
   • PRCB CN13-10 (LOCK) — the lock signal returned from the fan
   • Wiring location: 24-C
4. When FM2 is commanded ON, you should hear the fan start and feel airflow near the transfer belt cleaner area

For bizhub C220 / C280 / C360:

1. Command FM6 to run — monitor:
   • PRCB CN3-17 (REM) — drive command signal
   • PRCB CN3-18 (LOCK) — lock signal return

Interpreting the operation check results:

• Drive signal present (REM active) AND fan starts, airflow felt, LOCK signal transitions: Fan is functioning correctly. The original C2355 was caused by the debris or connector issue corrected in Steps 2–3. Run a test print to confirm
• Drive signal present (REM active) BUT fan does not start and LOCK stays HIGH: Fan is receiving the drive command but is not responding — the fan is seized or the internal feedback sensor has failed. Replace FM2/FM6/FM5 (Step 5)
• Drive signal present (REM active) AND fan is visibly spinning BUT LOCK stays HIGH: Fan blades are physically rotating but the internal Hall-effect feedback sensor has failed and is not generating lock pulses. Replace FM2/FM6/FM5 (Step 5)
• No drive signal present at fan connector even with operation check commanded ON: The PRCB or MFPB is not outputting the drive signal — check ICP continuity (Step 5) before replacing the board

Step 5 — Check ICP Continuity

When the motor operation check shows no drive signal at the fan connector, check the inline circuit protector before replacing the control board. A blown ICP is significantly cheaper to address than a full board replacement and is the most commonly missed step when there is no drive signal at the connector.

For bizhub C224 / C284 / C364 / C224e / C284e / C364e / C454 / C554 / C7822 / C7828:

1. Access the PRCB and locate ICP3 — refer to the service manual for the exact component location on the board
2. Test ICP3 continuity with a multimeter in continuity mode:
   • Continuity present → ICP3 is intact; fault is in the board drive circuit → replace PRCB (Step 6)
   • No continuity → ICP3 has blown
3. Before replacing the PRCB, confirm FM2 is not seized — a seized fan with a shorted motor coil is what blows ICP3. Test FM2 by spinning the blades by hand. If the fan is confirmed seized (Step 2), replace FM2 first, then address ICP3

For bizhub C220 / C280 / C360:

1. Locate PRCB ICP2 on the board
2. Test for continuity — no continuity confirms ICP2 has blown
3. Same precaution: confirm FM6 bearings are not seized before replacing the PRCB

For bizhub C452 / C552 / C652:

1. Locate PRCB ICP7
2. Test for continuity — no continuity confirms ICP7 has blown

Step 6 — Replace the Fan Motor (FM2 / FM6 / FM5 / FM11)

Replace the fan motor when:

• The blades are clean but the fan is seized or produces grinding/resistance when spun by hand
• The operation check shows drive signal present but the fan does not respond
• The fan is visibly spinning during the operation check but the LOCK signal stays HIGH (internal sensor failed)

1. Order the correct replacement fan for your model — fan part numbers and blade/frame dimensions differ between FM2 (C224/C284/C364 family), FM6 (C220/C280/C360), FM5 (C452/C552/C652 and C654/C754). Always confirm using your machine model number
2. Power OFF and unplug the machine
3. Before installing the new fan, clean the fan housing of any accumulated toner and dust — a clean housing prevents the replacement fan from immediately accumulating the same debris load that contributed to the original failure
4. Check the airflow direction arrow printed on the fan frame before installation — installing a fan in reverse pushes hot air back into the transfer belt cleaner area instead of exhausting it, which defeats the purpose of the fan and can cause heat-related image quality problems even though C2355 would clear
5. Install the replacement fan, ensuring the mounting is secure and the fan frame is properly seated in the housing
6. Reconnect the harness firmly — confirm the connector clicks into place at both the fan end and the relay/board end
7. Power on and run the fan operation check in service mode one final time — confirm the drive signal is present and the LOCK signal transitions correctly with the new fan before reassembling all covers
8. Run a test print and confirm C2355 does not return

Step 7 — Replace the PRCB or MFPB

Board replacement is the final step for C2355 and should only be performed after a confirmed-good fan, confirmed-good connectors, and intact ICPs still produce C2355 consistently.

• Replace PRCB — bizhub C224/C284/C364 family, C454/C554, C220/C280/C360, C452/C552/C652, C654/C754, C7822/C7828
• Replace MFPB — bizhub C227/C287/C367, C258/C308/C368, C458/C558/C658, 458e/558e/658e

Quick Reference — Troubleshooting by Symptom

Understanding C2355 Within the Cooling Fan Error Family

C2355 belongs to a broader group of cooling fan errors on the bizhub platform. Each code targets a specific fan. Understanding the family helps identify shared causes when multiple fan codes appear together:

• C2355 — Transfer belt cleaner cooling fan (FM2/FM6/FM5/FM11) failure to turn
• C5351 — Power supply cooling fan (FM1/M4/M21) failure to turn
• C5352 — Secondary cooling fan (FM2 on some model families) failure to turn
• C5353 — Imaging unit cooling fan failure to turn
• C5354 — Ozone ventilation fan failure to turn
• C5355 — Toner bottle cooling fan failure to turn
• C5356 — Main cooling fan failure to turn

C2355 appearing alongside another fan error code (e.g. C5351 or C5353) at the same time indicates a shared power supply fault or a PRCB/MFPB board-level power rail failure affecting multiple fan circuits simultaneously. In this scenario, check the common power rail and ICP continuity across all affected fan circuits before replacing individual fans or the board.

A single C2355 in isolation confirms the fault is specific to the transfer belt cleaner cooling fan circuit — the other fans are functioning normally. Focus exclusively on FM2/FM6/FM5 and its connector path.

Preventing C2355 From Recurring

• Clean the transfer belt cleaner fan during every PM visit — this fan is positioned in one of the highest toner-dust concentration areas of the machine. Toner from the belt cleaning process accumulates on the fan blades faster than most other fans in the machine. A 3-minute cleaning with compressed air at every PM visit is the single most effective prevention for C2355 on high-volume machines
• Reseat the FM2/FM6 connector during every PM visit — the fan connector is in an area subject to toner dust accumulation and thermal cycling. A 30-second reseat and visual inspection during routine maintenance prevents the gradual oxidation and contact degradation that causes intermittent C2355 events between planned service visits
• Replace the fan motor proactively on high-volume machines — the transfer belt cleaner fan runs continuously during every print job and has a finite bearing life. On machines processing above 15,000 pages per month in colour, consider replacing FM2/FM6 as part of the standard PM kit every 2–3 years rather than waiting for C2355. The fan is an inexpensive component compared to the diagnostic time for a service call
• Always check the airflow direction when installing a replacement fan — incorrect airflow direction is an avoidable installation error that produces a machine that clears C2355 but then develops heat-related image quality problems within days. Confirm the arrow on the fan frame before securing the mounting screws
• Replace FM2/FM6 before replacing the PRCB when ICP has blown — this sequence prevents the most expensive possible outcome of a C2355 repair: a blown ICP that is repaired on the PRCB, followed by immediate re-blowing from the still-seized fan, requiring a second board repair or replacement

Professional Technician Summary

Error Code C2355 on Konica Minolta bizhub machines is a transfer belt cleaner cooling fan failure, and it is one of the most straightforward error codes to diagnose and resolve on the platform. The component chain is short — fan, connector, ICP, board — and the failure modes are predictable.

Accumulated toner dust on the fan blades causing seizure is the leading field cause, particularly on machines running above 10,000 colour pages per month in environments with airborne toner contamination. Cleaning the fan takes five minutes and resolves this without any parts replacement.

Connector displacement after service visits is the second most common cause — and on the C220/C280/C360 specifically, the two-relay path means there are three connector points to check, not one. Missing the intermediate relay connector is the most common reason C2355 persists after a “connector check” on these models.

When the fan is confirmed clean and connectors are confirmed seated, the service mode operation check is the definitive next step — it distinguishes between a fan that won’t spin (replace fan), a fan spinning without lock signal feedback (replace fan), and no drive signal at all (check ICP, then board). This check prevents the expensive mistake of replacing a good fan when the fault is actually a blown ICP or board failure.