Error Code C2156 is a Rank B imaging engine fault generated when the machine detects that the 1st transfer pressure sensor (PS39) is turned OFF (unblocked) after the lapse of the given time after the 1st transfer pressure clutch (CL5) has turned OFF at the end of the pressing operation. In plain terms: the machine successfully completed the all-pressure state — the intermediate transfer belt (ITB) was confirmed in contact with all four photoconductor drums — but when the pressing operation ended and CL5 was deactivated, PS39 unexpectedly unblocked, indicating the belt mechanism drifted away from the confirmed all-pressure position without being commanded to retract.
C2156 is the inverse fault of C2153. Where C2153 fires because the belt fails to retract when commanded, C2156 fires because the belt retracts — or more precisely, because PS39 signals retraction — when it should be maintaining the all-pressure contact position after CL5 has been deactivated. The cam or sensing mechanism has moved into a state that does not correspond to the expected maintained all-pressure position.
C2156 belongs to the same five-code C215x family as C2152, C2153, C2154, and C2155. All five codes involve the same three components — the fusing motor (M3), the 1st transfer pressure clutch (CL5), and the 1st transfer pressure sensor (PS39) — and share the same remedy procedure sequence. The board architecture differs between model generations, introducing the EXCB and BASEB/CPUB layers on higher-end and newer-generation platforms. Identifying the correct model group and its associated connector paths is the mandatory first step before beginning any investigation.
| Field | Details |
|---|---|
| Error Code | C2156 |
| Description | Transfer belt spacing fault after all pressure established |
| Error Rank | B — machine halts all printing; requires technician intervention |
| Detection Condition | The 1st transfer pressure sensor (PS39) is turned OFF (unblocked) after the lapse of given time after the 1st transfer pressure clutch (CL5) turned OFF when the pressing operation is finished — the belt spacing (retraction) is detected when the all-pressure maintained position should be confirmed |
| Key Components — MFPB platform (C227/C287, C258/C308/C368) | Fusing motor (M3), 1st transfer pressure clutch (CL5), 1st transfer pressure sensor (PS39), MFP board (MFPB) |
| Key Components — MFPB+EXCB platform (C458/C558/C658) | Fusing motor (M3), 1st transfer pressure clutch (CL5), 1st transfer pressure sensor (PS39), MFP board (MFPB), Expansion control board (EXCB) |
| Key Components — BASEB+EXCB+CPUB platform (C360i/C300i/C250i, C450i/C550i/C650i, C750i) | Fusing motor (M3), 1st transfer pressure clutch (CL5), 1st transfer pressure sensor (PS39), Base board (BASEB), Expansion control board (EXCB), CPU board (CPUB) |
| Key Components — PRCB platform (C224/C284/C364 and -e variants) | Fusing motor (M3), 1st transfer pressure clutch (CL5), 1st transfer pressure sensor (PS39), Printer control board (PRCB) |
| PS39 I/O Signal — C227/C287 | MFPB CN7E<B>-13 (ON); Location: 22-C |
| PS39 I/O Signal — C258/C308/C368 | MFPB CN15EB-17 (ON); Location: 10-C |
| PS39 I/O Signal — C458/C558/C658 | MFPB CN15E (I/O); Location: 10-C |
| PS39 I/O Signal — C360i/C300i/C250i / C450i/C550i/C650i / C750i | BASEB CN13E-3 (ON); Location: 11-C (C360i/C250i/C300i) / 13-C (C450i/C550i/C650i) |
| PS39 I/O Signal — C224/C284/C364 / -e variants | PRCB CN13-7 (ON); Location: 24-C |
| CL5 Signal — C227/C287 | MFPB CN12E-12 (ON); Location: 5-C |
| CL5 Signal — C258/C308/C368 | MFPB CN15EA-18 (ON); Location: 8-C |
| CL5 Signal — C458/C558/C658 | EXCB CN8; Location: refer to service manual |
| CL5 Signal — C360i/C450i/C550i/C650i/C750i | EXCB CN14EX-9 (REM); Location: 17 to 18-P |
| CL5 Load Check — C360i/C450i/C550i/C650i/C750i | Check code: 24; Multi code: varies by model (see service mode reference table) |
| M3 Signal — C227/C287 | MFPB CN11E-11 (REM), MFPB CN11E-14 (FGP); Location: 3-C |
| M3 Signal — C258/C308/C368 / C458/C558/C658 | MFPB CN8E-9 (REM), MFPB CN8E-12 (LOCK); Location: 2-C |
| M3 Signal — C360i/C450i/C550i/C650i/C750i | BASEB CN19EA-6 to 10; Check code: 45 (C360i/C450i/C550i/C650i); Location: 1-C |
| M3 Signal — C224/C284/C364 / -e variants | PRCB CN2-9 (REM), PRCB CN2-12 (LOCK); Location: 27-I to J |
| MFPB Fuse — C227/C287 | MFPB F13E |
| MFPB Fuse — C258/C308/C368 / C458/C558/C658 | MFPB ICP2E |
| PRCB Fuse — C224/C284/C364 / -e variants | PRCB ICP3 |
| Related Codes | C2152 (transfer belt fault at initial position return), C2153 (transfer belt spacing fault at K pressure switching), C2154 (transfer belt contact fault at all pressure switching), C2155 (transfer belt contact fault after K pressure established) |
All Affected Models
C2156 applies to all bizhub colour models using the PS39 / CL5 / M3 transfer belt pressure architecture. The board architecture and connector paths differ significantly between model generations. Confirm the exact model group from the machine’s identification label before beginning any connector investigation.
| bizhub Models | PS39 Path | CL5 Path | M3 Connector | Board Architecture | Fuse |
|---|---|---|---|---|---|
| bizhub C227 / C287 | PS39 — relay CN24 — MFPB CN7E; signal: CN7E<B>-13 (ON); loc: 22-C | CL5 — relay CN29 — MFPB CN12E; signal: CN12E-12 (ON); loc: 5-C | MFPB CN11E; CN11E-11 (REM), CN11E-14 (FGP); loc: 3-C | MFPB | MFPB F13E |
| bizhub C258 / C308 / C368 | PS39 — relay CN113 — MFPB CN15EB; signal: CN15EB-17 (ON); loc: 10-C | CL5 — relay CN118 — MFPB CN15EA; signal: CN15EA-18 (ON); loc: 8-C | MFPB CN8E; CN8E-9 (REM), CN8E-12 (LOCK); loc: 2-C | MFPB | MFPB ICP2E |
| bizhub C458 / C558 / C658 | PS39 — relay CN113 — MFPB CN15E; signal: CN15E (I/O); loc: 10-C | CL5 — relay CN118 — EXCB CN8; loc: refer to service manual | MFPB CN8E; CN8E-9 (REM), CN8E-12 (LOCK); loc: 2-C | MFPB + EXCB | MFPB ICP2E |
| bizhub C360i / C300i / C250i | PS39 — relay CN113 — BASEB CN13E; signal: CN13E-3 (ON); loc: 11-C | CL5 — relay CN118 — EXCB CN14EX; signal: CN14EX-9 (REM); loc: 17 to 18-P; check code: 24 | BASEB CN19EA-6 to 10; check code: 45; loc: 1-C | BASEB + EXCB + CPUB | Refer to service manual |
| bizhub C450i / C550i / C650i | PS39 — relay CN113 — BASEB CN13E; signal: CN13E-3 (ON); loc: 13-C | CL5 — relay CN118 — EXCB CN14EX; signal: CN14EX-9 (REM); loc: 17 to 18-P; check code: 24 | BASEB CN19EA-6 to 10; check code: 45; loc: 1-C | BASEB + EXCB + CPUB | Refer to service manual |
| bizhub C750i | PS39 — relay CN113 — BASEB CN13E; signal: CN13E (I/O) | CL5 — relay CN118 — EXCB CN14EX; also check EXCB CN2EX — BASEB CN12E | Refer to service manual | BASEB + EXCB + CPUB | Refer to service manual |
| bizhub C224 / C284 / C364 | PS39 — relay CN113 — PRCB CN13; signal: CN13-7 (ON); loc: 24-C | CL5 — relay CN118 — PRCB CN13; signal: CN13-14 (ON); loc: 23 to 24-C | PRCB CN2; CN2-9 (REM), CN2-12 (LOCK); loc: 27-I to J | PRCB | PRCB ICP3 |
| bizhub C224e / C284e / C364e | PS39 — relay CN113 — PRCB CN13; signal: CN13-7 (ON); loc: 24-C | CL5 — relay CN118 — PRCB CN13; signal: CN13-14 (ON); loc: 23 to 24-C | PRCB CN2; CN2-9 (REM), CN2-12 (LOCK); loc: 27-I to J | PRCB | PRCB ICP3 |
| bizhub C454 / C554 | Refer to service manual | Refer to service manual | Refer to service manual | MFPB | Refer to service manual |
| bizhub C454e / C554e | Refer to service manual | Refer to service manual | Refer to service manual | MFPB | Refer to service manual |
ℹ️ CL5 load check multi-code values — C450i/C550i/C650i (Check code: 24): Multi code: 1, 2, 100, 101, 102, 104, 105, 106 (bizhub C650i); 1, 2, 101, 102, 105, 106 (bizhub C550i); 1, 2, 100, 102, 104, 106 (bizhub C450i). For bizhub C360i/C300i/C250i, use Check code: 24 and refer to the service manual for applicable multi codes.
What Does Error Code C2156 Mean?
To understand C2156 precisely, it is necessary to understand what the machine expects at the end of the all-pressure pressing operation. The pressing cycle proceeds as follows:
- The machine commands CL5 to engage, coupling M3’s rotation to the transfer belt pressure cam mechanism.
- The cam rotates from the retraction position toward the all-pressure position — the position at which the ITB is in contact with all four photoconductor drums (Y, M, C, K).
- PS39 detects the cam reaching the all-pressure position and turns ON (blocked). This is the confirmation event that the pressing operation was successful, which the machine requires before beginning the imaging sequence.
- The machine then turns OFF CL5. Since the cam is a self-locking mechanism — the pressure is maintained by the cam geometry holding the belt contact rollers in position, not by continuous CL5 engagement — CL5 deactivation does not cause the cam to retract. The belt should remain at the all-pressure position under the cam’s own mechanical retention.
- At this point, PS39 should remain ON (blocked), confirming the cam is still at the all-pressure position.
- C2156 fires if, after CL5 has turned OFF, PS39 turns OFF (unblocked) within the timeout period — meaning the cam has moved away from the all-pressure position without being commanded to retract.
The critical insight is that C2156 detects an unexpected spontaneous retraction of the cam from the all-pressure position after the pressing operation was completed and CL5 was deactivated. This is mechanically different from C2154 (cam never reached all-pressure) or C2153 (cam fails to retract when commanded). C2156 specifically means the cam did reach all-pressure, confirmed by PS39 turning ON, but then retreated without command.
The phrase “after the lapse of given time” in the detection condition specifies that C2156 is not fired immediately when PS39 turns OFF — there is a brief timeout window after CL5 deactivation during which transient PS39 state changes are tolerated. C2156 fires only when PS39 has been in the OFF (unblocked) state for longer than this window after CL5 turned OFF following the pressing operation.
ℹ️ C2156 vs C2155 — a key distinction: C2155 fires when PS39 is turned ON (blocked — pressure state) after the lapse of time following CL5 turning OFF when the release operation is finished. C2156 fires when PS39 is turned OFF (unblocked — retraction state) after the lapse of time following CL5 turning OFF when the pressing operation is finished. C2155 = unexpected pressure maintained after release operation. C2156 = unexpected spacing detected after pressing operation. Both involve a PS39 state that contradicts the expected cam position after CL5 deactivation, but in opposite directions.
The Role of M3 and the Cam Self-Locking Mechanism
On all affected model families, the fusing motor M3 provides the mechanical power for the transfer belt pressure cam through the electromagnetic clutch CL5. The cam mechanism is designed to be self-retaining: once the cam reaches the all-pressure or full-retraction positions, the cam geometry holds the mechanism in that position without requiring continuous CL5 engagement. CL5 is energized only during transitions between positions, then deactivated once the target position is confirmed by PS39.
C2156 occurring — the cam apparently leaving the all-pressure position spontaneously after CL5 deactivation — points to one of three mechanical failure categories:
- The cam did not reach a stable self-retaining geometry at the all-pressure position: The cam stopped at a position near but not fully at the locking geometry, and the spring load of the contact rollers pushed it back to an intermediate position that PS39 interprets as retraction.
- The cam’s self-retaining mechanism has worn or failed: On high-volume machines, the cam locking features (detent, latch, or geometric lock) wear with accumulated cycles, reducing or eliminating the mechanical retention force that holds the cam at the all-pressure position against the spring load.
- PS39 is producing a spurious OFF signal while the cam is actually at the all-pressure position: Sensor contamination, misalignment, a loose connector, or a failed sensor can cause PS39 to report the retraction state even when the cam has not moved. This is a sensor reporting error, not a true cam movement, but it produces an identical C2156 from the machine’s perspective.
Common Causes of C2156
- Loose or disconnected connector in the PS39 signal path — the most frequent cause. PS39 routes through an intermediate relay connector (CN24 on C227/C287; CN113 on C258 and later models) before reaching the main control board. A connector that is partially seated can produce intermittent signal dropouts that the control board interprets as PS39 turning OFF after CL5 deactivation, generating C2156 even when the cam is physically stable at the all-pressure position. On the BASEB-platform models (C360i/C450i/C550i/C650i/C750i), also check the EXCB CN2EX to BASEB CN12E communication connector, as a loose EXCB-to-BASEB link can corrupt sensor signal reporting.
- PS39 sensor contamination or misalignment. Toner and paper dust accumulate on PS39’s optical faces progressively with every print cycle. A contaminated sensor can produce intermittent or persistent false OFF transitions. Physical misalignment — from a rear panel reinstallation, ITB unit removal, or rough jam clearance — can cause PS39 to lose sight of the cam flag even when the cam is at the all-pressure position, producing persistent C2156 regardless of cam mechanical condition.
- Worn or damaged cam self-retention mechanism. The cam that drives the ITB contact rollers is designed to hold its position at the all-pressure point without requiring continuous CL5 power. On high-volume machines with many accumulated pressure cycles, the cam’s locking geometry, a detent spring, or a latch mechanism can wear to the point where the spring force of the ITB contact rollers pushes the cam back from the all-pressure position after CL5 deactivates. The cam physically retracts, PS39 turns OFF, and C2156 is generated. This is a genuine mechanical failure requiring cam assembly replacement.
- Loose or disconnected connector in the CL5 clutch signal path. A loose CL5 connector (at relay CN29/CN118 or at the board end) can cause CL5 to deactivate prematurely — before the cam has fully reached the self-retaining all-pressure position. The cam reaches a partial position, PS39 may briefly turn ON, CL5 then deactivates unexpectedly, and the cam spring-loads back toward retraction as PS39 turns OFF — C2156 is generated. This failure mode also often produces C2154 (contact fault) or C2152 (initial position fault) alongside C2156 on the same fault event.
- M3 drive coupling deterioration. If M3’s coupling to the pressure cam drive train has developed looseness or slippage, the cam may not reach the full self-retaining geometry within the allowed timing window. CL5 deactivates at the end of the pressing command period, the cam is at a partial-pressure position that is not fully self-retaining, and spring forces retract the cam — PS39 turns OFF and C2156 fires. Inspect the M3 drive coupling if the M3 operation check passes (motor runs) but C2156 still occurs.
- Damaged harness between PS39/CL5 and their relay connectors or the control board. A fractured wire in the PS39 signal path — producing an intermittent open circuit — will cause PS39’s signal to drop out transiently, generating C2156 with no mechanical cam movement at all. Harness damage is more likely on machines where rear panels have been removed and reinstalled multiple times, where the harness has been pinched at a cable clip, or where toner or moisture has degraded the insulation.
- MFPB fuse blown (F13E on C227/C287; ICP2E on C258/C308/C368/C458/C558/C658) or PRCB fuse blown (ICP3 on C224/C284/C364 series). A blown supply fuse on the main control board can cause PS39 to lose its supply voltage, producing a persistent OFF state that appears as a spontaneous retraction signal after CL5 deactivates. Fuse conduction must be confirmed before the main board is condemned.
- EXCB failure — C458/C558/C658 and BASEB-platform models. On models where CL5 routes through the EXCB, a partially failed EXCB output can cause CL5 to deactivate at incorrect timing, not giving M3 sufficient time to drive the cam fully into the self-retaining all-pressure position. The result is an incompletely locked cam that spring-retracts after CL5 loss, triggering C2156.
- CPUB improper installation — BASEB-platform models (C360i/C450i/C550i/C650i/C750i). On machines with the BASEB/EXCB/CPUB architecture, a CPUB that is not correctly seated in its slot can disrupt the board interconnection and corrupt both sensor signal reading and clutch command timing, producing C2156 and potentially other C215x codes simultaneously. The CPUB seating check is a documented remedy step for these models.
- MFPB, EXCB, or BASEB board-level failure. If the main control board’s PS39 input circuit produces spurious OFF readings, or its CL5 output deactivates at incorrect timing due to an internal driver fault, C2156 is generated without any mechanical cam movement. Board replacement is always the final escalation step after all mechanical, connector, sensor, and fuse causes have been confirmed or eliminated.
Quick Reference — Troubleshooting by Symptom
| Symptom | Most Likely Cause | First Action |
|---|---|---|
| C2156 on the first colour job after power-on; machine previously operated normally | PS39 connector (relay CN24/CN113 or board-end) loose; PS39 contaminated | Reseat all connectors in PS39 signal path; clean PS39 sensor faces; perform PS39 I/O check |
| C2156 intermittent — clears on power cycle, returns after several colour jobs | Intermittent connector in PS39 signal path (relay connector most likely); partially worn cam retention mechanism under thermal load | Reseat all relay and board-end connectors; flex harness while monitoring; inspect cam retention mechanism |
| C2156 consistent on every full-colour job but mono jobs (K-only) succeed | Cam self-retention mechanism worn — fails to hold all-pressure position once CL5 deactivates; PS39 misaligned at all-pressure position | Inspect cam physical retention; confirm PS39 is correctly aligned to flag at all-pressure cam position; check cam assembly for wear |
| C2156 accompanied by C2154 (contact fault) on the same fault event | CL5 connector intermittent — CL5 deactivates prematurely before cam reaches self-retaining position; cam does not fully seat into locking geometry | Reseat CL5 relay connector (CN29/CN118) and board-end connector; perform CL5 operation/load check; inspect cam for partial engagement at all-pressure position |
| C2156 with multiple C215x codes simultaneously (C2152, C2153, C2154, C2155, C2156) | CL5 failed completely; cam mechanism seized or severely worn; EXCB failure (on applicable models) | Perform CL5 operation/load check; inspect cam mechanism manually; replace CL5; check EXCB on C458/C558/C658 and BASEB-platform models |
| C2156 immediately after rear-panel or ITB-area service was performed | PS39 physically displaced during reassembly; PS39 relay connector (CN24/CN113) not fully reseated after panel removal | Confirm PS39 mounting and alignment; reseat all PS39 path connectors; perform PS39 I/O check |
| C2156 alongside a fusing fault code | M3 failure — both fusing and transfer pressure cam share M3 drive; cam cannot reach full self-retaining position | Perform M3 operation/load check; replace M3 if confirmed failed |
| C2156 on BASEB-platform model (C360i/C450i/C550i/C650i/C750i) with EXCB CN2EX — BASEB CN12E connector unseated | EXCB-to-BASEB communication fault — sensor signal or clutch command corrupted in transit between boards | Reseat EXCB CN2EX — BASEB CN12E connector; also check CPUB seating; perform PS39 I/O check and CL5 load check after connector reseat |
| C2156 persists after confirmed-good connectors, clean PS39, functioning CL5, and intact cam | MFPB/PRCB fuse blown; EXCB failure; board-level PS39 input or CL5 output failure | Check MFPB F13E or ICP2E / PRCB ICP3 conduction; on EXCB models replace EXCB before MFPB/BASEB |
Step-by-Step Diagnostic and Repair Procedure
⚠️ Warning: Switch the machine OFF at the main power switch and disconnect the power cord before performing any connector checks, mechanical inspections, or component replacements in the imaging engine area. Allow at least 20 minutes after power-off before accessing components near the fusing unit — surface temperatures in this area are hazardous during and immediately after operation. Do not touch the ITB surface with bare hands or tools; finger oils and tool contact cause permanent image quality damage to the belt coating. Do not use compressed air directly on the ITB surface.
Step 1 — Confirm the Model Group and Record All Active Codes
- Confirm the bizhub model from the machine’s identification label and establish the correct model group (C227/C287 MFPB-only; C258/C308/C368 MFPB-only; C458/C558/C658 MFPB+EXCB; C360i/C300i/C250i or C450i/C550i/C650i or C750i BASEB+EXCB+CPUB; C224/C284/C364 or -e variants PRCB-only). This determines every connector reference and board check in the remedy sequence.
- Record all active error codes. The pattern of C215x codes present provides diagnostic direction:
- C2156 alone — most likely a PS39 signal path fault (connector, contamination, or sensor) or a cam self-retention wear issue.
- C2154 + C2156 together — strongly suggests a CL5 intermittent deactivation causing the cam to fail to reach its self-retaining geometry; also consider M3 drive coupling slippage.
- C2152 + C2153 + C2154 + C2155 + C2156 simultaneously — CL5 complete failure or severely seized cam mechanism; investigate CL5 and the cam before individual sensors and connectors.
- C2156 + a fusing fault code — M3 failure as the primary suspect.
- Note whether C2156 appeared on the machine’s first colour print of the session (power-on) or only after the machine had been printing for some time. A thermal-dependent fault that only emerges after the machine is warm points to a marginal CL5 clutch or a cam retention mechanism that loses holding force at operating temperature.
Step 2 — Inspect and Reseat All Connectors in the PS39 and CL5 Signal Paths
- Power the machine OFF and disconnect the power cord. Allow at least 20 minutes for the fusing area to cool.
- Access the imaging engine area via the appropriate side or rear panels per the service manual for your model.
- Reseat all connectors in the PS39 signal path — at every connection point from sensor to board:
- Connector at the PS39 sensor body.
- Relay connector:
- C227 / C287: relay CN24
- C258 / C308 / C368 / C458 / C558 / C658 / C360i / C300i / C250i / C450i / C550i / C650i / C750i / C224 / C284 / C364 / -e variants: relay CN113
- Board-end connector:
- C227 / C287: MFPB CN7E
- C258 / C308 / C368: MFPB CN15EB
- C458 / C558 / C658: MFPB CN15E
- C360i / C300i / C250i / C450i / C550i / C650i / C750i: BASEB CN13E
- C224 / C284 / C364 / -e variants: PRCB CN13
- Reseat all connectors in the CL5 signal path:
- Connector at the CL5 clutch body.
- Relay connector:
- C227 / C287: relay CN29
- C258 / C308 / C368 / C458 / C558 / C658 / C360i / C300i / C250i / C450i / C550i / C650i / C750i / C224 / C284 / C364 / -e variants: relay CN118
- Board-end connector:
- C227 / C287: MFPB CN12E
- C258 / C308 / C368: MFPB CN15EA
- C458 / C558 / C658: EXCB CN8
- C360i / C300i / C250i / C450i / C550i / C650i / C750i: EXCB CN14EX
- C224 / C284 / C364 / -e variants: PRCB CN13
- For BASEB-platform models (C360i/C300i/C250i, C450i/C550i/C650i, C750i) only — also reseat the EXCB-to-BASEB communication connector: EXCB CN2EX — BASEB CN12E. A loose EXCB-to-BASEB connector corrupts both CL5 command transmission and PS39 signal reading, producing C2156 even when all individual component connectors are fully seated.
- Inspect all pins at every connector in both paths for bent contacts, pushed-back pins, toner contamination, or corrosion. Clean with isopropyl alcohol and a soft brush where contamination is found.
- Reconnect power and attempt a full-colour test print. If C2156 does not recur, the fault was a connector seating issue — document and close.
Step 3 — Check CPUB Seating (BASEB-Platform Models Only)
- On models with the BASEB/EXCB/CPUB architecture (C360i/C300i/C250i, C450i/C550i/C650i, C750i), confirm the CPUB is correctly and fully seated in its board slot.
- Power the machine OFF and disconnect the power cord. Access the CPUB per the service manual for your model.
- Remove the CPUB and reseat it firmly, confirming all edge connector contacts are fully engaged. A CPUB that is partially inserted — even by one row of connector contacts — can disrupt the BASEB/EXCB system in ways that produce spurious C215x code groups including C2156.
- Reconnect power and test before proceeding to sensor and mechanical checks.
Step 4 — Inspect and Clean PS39 and Inspect the Cam Flag Alignment
- Power the machine OFF and disconnect the power cord.
- Locate PS39 (1st transfer pressure sensor) in the transfer belt pressure cam area. Refer to the wiring diagram location for your model group (22-C for C227/C287; 10-C for C258/C308/C368/C458/C558/C658; 11-C for C360i/C300i/C250i; 13-C for C450i/C550i/C650i).
- Inspect the PS39 sensor faces for toner dust, paper fiber, or other contamination. Clean with a dry lint-free cloth or a cotton swab. Do not use solvents on the sensor body plastic.
- Locate the PS39 actuator flag — the cam flag that enters the PS39 beam path when the cam is at the all-pressure position. Inspect:
- The flag is present and undamaged.
- The flag is correctly aligned to fully block the PS39 beam when the cam is at the all-pressure position. A flag that is bent outward from the sensor axis — even by a few degrees — may not fully block the beam when the cam reaches the all-pressure position, causing PS39 to report an intermediate state that is interpreted as retraction after CL5 deactivates.
- The flag moves freely without catching on adjacent components.
- Manually position the cam to what appears to be the all-pressure position (power off) and observe whether the PS39 flag fully enters the sensor beam. If there is any doubt about flag alignment, compare against the service manual’s layout drawing for the transfer belt pressure mechanism (location reference S.xx in the service manual for C215x codes).
- With connectors reseated, reconnect power and perform the PS39 I/O check in service mode:
- C227 / C287: Control signal: MFPB CN7E<B>-13 (ON); Location: 22-C
- C258 / C308 / C368: Control signal: MFPB CN15EB-17 (ON); Location: 10-C
- C458 / C558 / C658: Control signal: MFPB CN15E (I/O); Location: 10-C
- C360i / C300i / C250i / C450i / C550i / C650i: Control signal: BASEB CN13E-3 (ON); Location: 11-C (C360i/C300i/C250i) or 13-C (C450i/C550i/C650i)
- C224 / C284 / C364 / -e variants: Control signal: PRCB CN13-7 (ON); Location: 24-C
- Manually insert and withdraw a slip of paper or thin card into the PS39 beam path and confirm the signal transitions between ON (blocked) and OFF (unblocked). If no transition occurs with a clean sensor and confirmed connector, PS39 has failed — replace it. Refer to the service manual for the correct PS39 part number for your model.
Step 5 — Inspect the Transfer Belt Pressure Cam Self-Retention Mechanism
- Power the machine OFF and disconnect the power cord.
- Access the transfer belt pressure cam mechanism. Refer to the service manual’s layout drawing for the transfer belt pressure fault codes (section S.xx for C215x codes) to locate the cam assembly for your specific model.
- With power disconnected, manually rotate the cam to the position that corresponds to the all-pressure state. Observe whether the cam holds this position when released, or whether the spring load from the ITB contact rollers causes it to back off toward an intermediate position. A cam that does not hold its all-pressure position under spring load without CL5 engaged has a worn or damaged self-retention feature (detent, latch, or geometric lock surface) and requires cam assembly replacement.
- Also inspect the cam for:
- Visible wear on the cam locking surfaces or detent features.
- A missing, weakened, or incorrectly positioned detent spring.
- Debris (toner cakes, paper fragments) lodged in the cam travel path that could prevent the cam from fully reaching the locking geometry at the all-pressure position.
- If the cam mechanism is worn or damaged, refer to the service manual for the correct cam assembly replacement part number and procedure for your model.
Step 6 — Perform the CL5 Operation Check / Load Check and Inspect CL5 Clutch
- Reconnect power and enter Service Mode.
- Perform the CL5 operation check or load check:
- C227 / C287: Control signal: MFPB CN12E-12 (ON); Location: 5-C
- C258 / C308 / C368: Control signal: MFPB CN15EA-18 (ON); Location: 8-C
- C458 / C558 / C658: Control signal: EXCB CN8; refer to service manual for signal pin
- C360i / C300i / C250i / C450i / C550i / C650i / C750i: Check code: 24; Control signal: EXCB CN14EX-9 (REM); Location: 17 to 18-P. (Multi code varies by model — see the summary table.)
- C224 / C284 / C364 / -e variants: Control signal: PRCB CN13-14 (ON); Location: 23 to 24-C
- Listen for the characteristic click of the electromagnetic clutch engaging. If no engagement sound is heard while the operation check is active, CL5 is not engaging despite the command signal — the coil may be open, or the clutch plate has failed. If CL5 consistently fails to engage, the cam never reaches the self-retaining all-pressure position, and C2154 and C2156 may both result from the same root cause.
- Also consider a marginal CL5 that engages but slips under load, causing the cam to reach only a partial-pressure position that backs off after CL5 deactivates. A slipping clutch may pass the operation check at low load but fail under the full spring-load of the ITB contact rollers during a normal print cycle. If marginal CL5 is suspected, replace CL5 and monitor across several print cycles.
- If CL5 fails the operation check after the connector is confirmed seated, replace CL5. Refer to the service manual for the CL5 replacement procedure for your model.
Step 7 — Perform the M3 Operation Check / Load Check
- Reconnect power and enter Service Mode.
- Perform the M3 operation check or load check:
- C227 / C287: Control signal: MFPB CN11E-11 (REM), MFPB CN11E-14 (FGP); Location: 3-C
- C258 / C308 / C368 / C458 / C558 / C658: Control signal: MFPB CN8E-9 (REM), MFPB CN8E-12 (LOCK); Location: 2-C
- C360i / C300i / C250i / C450i / C550i / C650i: Check code: 45; Multi code: refer to service manual for model-specific values; Control signal: BASEB CN19EA-6 to 10; Location: 1-C
- C224 / C284 / C364 / -e variants: Control signal: PRCB CN2-9 (REM), PRCB CN2-12 (LOCK); Location: 27-I to J
- M3 should run smoothly during the operation check. The LOCK signal (or FGP on C227/C287) confirms the motor is generating its frequency generator output, indicating correct rotation. Confirm M3’s mechanical drive coupling to the pressure cam drive train is intact — a coupling that has developed play or slippage allows M3 to run electrically while delivering insufficient torque to drive the cam fully into the self-retaining position.
- If M3 fails the operation check, replace M3. Refer to the service manual for the M3 replacement procedure and part number for your model.
Step 8 — Check Control Board Fuse Conduction
- Power the machine OFF and disconnect the power cord.
- Access the main control board and locate the protective fuse for the CL5/PS39 supply circuit:
- C227 / C287: MFPB F13E
- C258 / C308 / C368 / C458 / C558 / C658: MFPB ICP2E
- C224 / C284 / C364 / -e variants: PRCB ICP3
- BASEB-platform models (C360i/C450i/C550i/C650i/C750i): Refer to the service manual for the applicable protective fuse or ICP designation on the BASEB or EXCB for the CL5 and PS39 supply circuits.
- Test conduction with a multimeter in continuity mode. An open circuit (no continuity) confirms a blown fuse. Replace with an identical rated device only.
- Before reassembly, investigate why the fuse blew — a blown fuse indicates an overcurrent event caused by a shorted CL5 coil, a short in the PS39 supply harness, or a board internal fault. A replacement fuse installed without correcting the short will blow again immediately.
Step 9 — Replace EXCB, CPUB, MFPB/PRCB/BASEB in Escalation Order
- Replace components in the following escalation order, verifying resolution after each replacement before proceeding:
- On C458/C558/C658: Replace EXCB first (CL5 routes through EXCB CN8); then replace MFPB as the final step.
- On C360i/C300i/C250i, C450i/C550i/C650i, C750i: Replace EXCB first (EXCB CN14EX drives CL5 and routes to BASEB); replace CPUB second if EXCB replacement does not resolve; replace BASEB as the final step.
- On C227/C287, C258/C308/C368: Replace MFPB as the sole board-level step.
- On C224/C284/C364 / -e variants: Replace PRCB as the sole board-level step.
- Photograph all connector positions on the existing board before removal. Reinstall all harnesses and connectors in the same positions on the replacement board. Confirm each connector is fully locked before powering on.
- After board replacement, perform the PS39 I/O check, CL5 operation/load check, and M3 operation/load check in service mode to confirm the replacement board drives and reads all components correctly before running a full-colour test print.
Service Mode Reference — PS39, CL5, and M3 Checks by Model Group
| Model Group | Component | Check Code | Multi Code | Control Signal | Location |
|---|---|---|---|---|---|
| C227 / C287 | PS39 (I/O check) | — | — | MFPB CN7E<B>-13 (ON) | 22-C |
| C227 / C287 | CL5 (operation check) | — | — | MFPB CN12E-12 (ON) | 5-C |
| C227 / C287 | M3 (operation check) | — | — | MFPB CN11E-11 (REM), MFPB CN11E-14 (FGP) | 3-C |
| C258 / C308 / C368 | PS39 (I/O check) | — | — | MFPB CN15EB-17 (ON) | 10-C |
| C258 / C308 / C368 | CL5 (operation check) | — | — | MFPB CN15EA-18 (ON) | 8-C |
| C258 / C308 / C368 | M3 (operation check) | — | — | MFPB CN8E-9 (REM), MFPB CN8E-12 (LOCK) | 2-C |
| C458 / C558 / C658 | PS39 (I/O check) | — | — | MFPB CN15E (I/O) | 10-C |
| C458 / C558 / C658 | CL5 (operation check) | — | — | EXCB CN8 (refer to service manual for pin) | Refer to SM |
| C458 / C558 / C658 | M3 (operation check) | — | — | MFPB CN8E-9 (REM), MFPB CN8E-12 (LOCK) | 2-C |
| C360i / C300i / C250i | PS39 (I/O check) | — | — | BASEB CN13E-3 (ON) | 11-C |
| C360i / C300i / C250i | CL5 (load check) | 24 | Refer to service manual | EXCB CN14EX-9 (REM) | 17 to 18-P |
| C360i / C300i / C250i | M3 (load check) | 45 | Refer to service manual | BASEB CN19EA-6 to 10 | 1-C |
| C450i / C550i / C650i | PS39 (I/O check) | — | — | BASEB CN13E-3 (ON) | 13-C |
| C450i | CL5 (load check) | 24 | 1, 2, 100, 102, 104, 106 | EXCB CN14EX-9 (REM) | 17 to 18-P |
| C550i | CL5 (load check) | 24 | 1, 2, 101, 102, 105, 106 | EXCB CN14EX-9 (REM) | 17 to 18-P |
| C650i | CL5 (load check) | 24 | 1, 2, 100, 101, 102, 104, 105, 106 | EXCB CN14EX-9 (REM) | 17 to 18-P |
| C450i / C550i / C650i | M3 (load check) | 45 | Refer to service manual for model-specific multi codes | BASEB CN19EA-6 to 10 | 1-C |
| C750i | PS39 (I/O check) | — | — | BASEB CN13E (I/O) | Refer to SM |
| C750i | CL5 (load check) | 24 | Refer to service manual | EXCB CN14EX-9 (REM) | 17 to 18-P |
| C750i | M3 (load check) | 45 | Refer to service manual | Refer to service manual | Refer to SM |
| C224 / C284 / C364 / -e variants | PS39 (I/O check) | — | — | PRCB CN13-7 (ON) | 24-C |
| C224 / C284 / C364 / -e variants | CL5 (operation check) | — | — | PRCB CN13-14 (ON) | 23 to 24-C |
| C224 / C284 / C364 / -e variants | M3 (operation check) | — | — | PRCB CN2-9 (REM), PRCB CN2-12 (LOCK) | 27-I to J |
Understanding C2156 in the Context of the C215x Code Family
C2156 is the last code in the five-member C215x transfer belt pressure fault group. Understanding each code’s detection direction and cam phase prevents wasted investigation:
- C2152 — Transfer belt fault at initial position return — PS39 cannot detect either direction of cam transition during the machine’s power-on initial position return cycle. Both retraction-to-pressure and pressure-to-retraction transitions fail. The most severe member: implies CL5 total failure or cam mechanical seizure.
- C2153 — Transfer belt spacing fault at K pressure switching — PS39 does not detect the switch from pressure to retraction (does not turn OFF) after CL5 engages during the K-pressure-to-retraction command. The cam commanded to retract did not retract.
- C2154 — Transfer belt contact fault at all pressure switching — PS39 does not detect the switch from retraction to pressure (does not turn ON) after CL5 engages during the all-pressure command. The cam commanded to make contact did not make contact.
- C2155 — Transfer belt contact fault after K pressure established — PS39 turns ON (blocked — pressure state) after the lapse of time following CL5 turning OFF at the end of the release operation. Unexpected pressure maintained after the release sequence.
- C2156 — Transfer belt spacing fault after all pressure established — this article. PS39 turns OFF (unblocked — retraction state) after the lapse of time following CL5 turning OFF at the end of the pressing operation. Unexpected spacing detected after the pressing operation; the belt has separated from the all-pressure maintained position without command.
C2155 and C2156 are mirror conditions: C2155 detects unexpected pressure (cam stays in pressure when it should be released), and C2156 detects unexpected spacing (cam returns from pressure when it should be maintained). Both fire after CL5 has deactivated, during the phase when the cam should be passively self-retaining at its target position. Both point to either a sensor/connector false-reading or a mechanical cam retention failure.
Rank B Reset Procedure
C2156 is classified as Rank B. The machine halts all printing — both colour and monochrome — and cannot resume until the fault is resolved. A power cycle may temporarily clear C2156 if the fault is intermittent (for example, a marginal connector that reseats slightly on power-off), but the code will return at the next all-pressure switching event if the root cause has not been corrected.
- After completing the repair, power the machine OFF at the main power switch.
- Wait at least 10 seconds for all circuits to fully discharge and the pressure cam mechanism to settle.
- Power the machine ON and observe the control panel during startup initialisation. The transfer belt pressure mechanism performs an initial position return cycle at startup — C2156 occurring during startup initialisation indicates the cam self-retention issue is present even at rest and points directly to a cam mechanical or PS39 alignment fault.
- Submit a full-colour test print. Observe that C2156 does not appear as the machine transitions to the all-pressure state for colour printing. Confirm PS39 transitions correctly (confirmed by the machine completing the print without fault).
- Submit a minimum of 10 consecutive full-colour sheets and then switch to a mono job and back to a colour job, confirming the machine correctly cycles between K-only and all-pressure states multiple times without generating C2156 or any other C215x code.
- On machines where the fault was thermal-dependent (only occurring after warm-up), allow the machine to reach full operating temperature and repeat the mono-to-colour switching test before signing off the repair.
Preventive Maintenance Recommendations
- Reseat relay connectors CN24/CN113 (PS39 path) and CN29/CN118 (CL5 path) at every PM visit. These relay connectors in the imaging engine area are subject to vibration from the paper transport mechanism and accumulate progressive loosening. A relay connector reseat takes under a minute at PM and is the single most effective preventive action against both C2156 and its sibling C2154.
- On BASEB-platform models, also reseat EXCB CN2EX — BASEB CN12E and check CPUB seating at every PM visit. This inter-board connection carries both CL5 commands and PS39 signal data. A loose EXCB-to-BASEB connector is a common source of intermittent C215x codes across the C360i/C450i/C550i/C650i/C750i platform and is frequently overlooked by technicians focused only on the sensor-end connectors.
- Clean PS39 at every PM visit. PS39 sits adjacent to the imaging section and accumulates toner at every print cycle. A brief cleaning of the sensor faces during PM prevents the gradual contamination buildup that eventually causes spurious OFF transitions and C2156.
- Inspect the transfer belt pressure cam self-retention mechanism during major PM on high-volume machines. The cam locking features wear with accumulated pressure cycles on high-page-count machines. Including a physical check of the cam at the all-pressure position — confirming it holds without CL5 power — during major PM identifies worn cams before they produce C2156 in production. Replace the cam assembly if it fails to self-retain under light spring load.
- After any ITB replacement or rear-panel access, verify PS39 alignment and all connector seating before closing up. ITB replacement and rear-panel service are the most common trigger events for C2156 appearing immediately after a service visit. A mandatory connector verification and PS39 alignment check as the final step before reassembly prevents a preventable callback.
- Monitor for C2156 during the first full-colour print run after replacing CL5. A new CL5 requires its coil to be correctly energised during the installation validation. A replacement CL5 that was not fully seated on its shaft or not correctly reconnected will produce C2154 and C2156 on the first print cycle after service, which is avoidable with a single-sheet colour test print before returning the machine to the customer.
Professional Technician Summary
Error Code C2156 detects unexpected belt spacing — PS39 turning OFF — after the all-pressure pressing operation has been confirmed and CL5 has been deactivated. Unlike C2154, which fires because the belt never made contact, C2156 fires because contact was successfully made but subsequently lost without a retraction command. This positional paradox points to either a sensor reporting error (PS39 connector or contamination) or a mechanical cam retention failure — the two most productive diagnostic directions.
In the field, the majority of C2156 calls are resolved by reseating the relay connectors (CN24/CN113 for PS39; CN29/CN118 for CL5), cleaning PS39, and — on BASEB-platform models — reseating the EXCB CN2EX to BASEB CN12E inter-board connector. These actions take under 15 minutes and address the root cause of most C2156 presentations without component replacement.
When mechanical investigation is required, the focus should be on whether the cam physically holds the all-pressure position after CL5 is deactivated. A cam that springs back from the all-pressure position under the ITB contact roller load — detectable by manually positioning the cam and releasing it with power off — confirms worn cam self-retention and requires cam assembly replacement regardless of PS39, CL5, or board condition.
When C2156 appears together with C2154, C2153, or multiple C215x codes simultaneously, investigate CL5 engagement and the cam mechanism as shared root causes before treating the individual codes as independent faults — a single failed or marginally engaged CL5 can produce the entire C215x code set by preventing any cam transition from completing correctly.