Jam Code 31-01 is a registration section primary misfeed on Konica Minolta bizhub machines. Konica Minolta service documentation classifies 31-xx codes under the heading Misfeed at Registration Section — a category that is narrower and more specific than it first appears. By the time a fault can be classified as 31-01, the paper has already been confirmed to have arrived at the registration sensor correctly and on time (the domain of the 20-xx vertical transport codes), and the WTEN image-write authorization has already been confirmed issued (the domain of the -40 codes). 31-01 addresses the step that happens immediately after both of those: the registration clutch (CL4) itself failing to complete its commanded engagement within the expected timing window. This is a fault in the registration drive mechanism’s own operation — a mechanical/electrical clutch engagement failure — occurring after every upstream condition for a successful print cycle has already been satisfied.

The official Konica Minolta description states precisely:

After the image write start signal permission (WTEN) was issued and the registration clutch (CL4) was commanded to engage, the clutch did not complete engagement within the specified timing window. The registration drive mechanism did not confirm successful engagement.

Translated into field language: everything that precedes this point in the print cycle has already gone correctly. The paper fed from its source, transported through the vertical transport section, arrived at the registration sensor on time, formed the correct registration loop, and the print controller confirmed the imaging section was ready and issued WTEN. The engine board then commands CL4 — the registration clutch — to engage, which should drive the registration rollers and begin advancing the paper toward the second transfer section. 31-01 fires when this specific command does not produce a confirmed engagement within the expected window — the clutch either did not engage at all, or engaged only partially, in a way the engine board’s own monitoring can detect as an engagement failure before the question of where the paper subsequently went (or didn’t go) even becomes relevant.

This makes 31-01 the narrowest and most upstream of the registration-area-adjacent fault codes covered across this series, and it sits at a very specific point in the diagnostic sequence relative to its neighbors:

• 20-01 / 20-02 (vertical transport codes) — address whether paper successfully arrived at the registration sensor at all, and on time. Both are excluded as causes by the time 31-01 fires, since arrival is a precondition for the loop-forming and WTEN sequence that precedes CL4 commanding
• The -40 WTEN codes — address whether the board-level authorization to proceed was issued at all. This is also excluded as a cause by the time 31-01 fires, since WTEN issuance is what triggers the CL4 command in the first place
• 31-01 — addresses whether the CL4 clutch itself, once commanded, actually completed engagement. This is a question about the clutch mechanism’s own function — coil, armature, spring, and mechanical engagement surfaces — independent of anything about paper transport or board communication
• 30-01 (second transfer section) — addresses whether the paper, after CL4 successfully engaged and began driving it, actually reached the next downstream sensor. This is excluded as a question by the time 31-01 fires, because 31-01 means CL4’s own engagement was never confirmed successful in the first place — the paper’s subsequent transport is not yet a relevant question

In short: 31-01 is a clutch mechanism fault, not a transport fault and not a board-communication fault. A technician who receives a 31-01 call and begins by inspecting vertical transport rollers, checking firmware versions, or investigating the second transfer section is investigating the wrong systems entirely. The diagnostic scope for 31-01 is narrow and specific: the CL4 clutch itself, its drive circuit, and the mechanical registration roller components it engages.

Field	Details
Jam Code	31-01
KM Category Heading	Misfeed at Registration Section — scoped specifically to the registration clutch (CL4) engagement event itself, occurring after paper arrival, loop forming, and WTEN issuance have all already been confirmed successful. Not a transport-timing fault and not a board-communication fault
What is confirmed functional when 31-01 fires	Source tray feed, vertical transport, registration sensor arrival timing, registration loop forming, and the complete WTEN handshake between the print controller and engine board. All of this preceded and enabled the CL4 command that subsequently failed. None of these systems require investigation for 31-01
Critical distinction from 20-01 / 20-02	20-01/20-02 concern whether paper reached the registration sensor at all, or on time. 31-01 occurs entirely after that question is settled — paper has already arrived correctly, and the fault is in what happens next (CL4 engagement), not in how the paper got there
Critical distinction from the -40 WTEN codes	The -40 codes mean WTEN was never issued — the imaging section was not confirmed ready, and CL4 was never even commanded. 31-01 means WTEN WAS issued and CL4 WAS commanded — the fault is that the commanded engagement did not complete, a downstream event from where the -40 codes occur
Critical distinction from 30-01	30-01 means CL4 successfully engaged and paper began transporting toward the second transfer section, but failed to arrive at the next sensor — a transport fault occurring after successful clutch engagement. 31-01 means CL4’s own engagement was never confirmed successful in the first place — a mechanism fault occurring before any question of subsequent paper transport is even relevant
Critical distinction from 10-04’s registration-clearance logic	10-04 (documented elsewhere in this series, scoped to bypass tray feeds) addresses a scenario where CL4 fires and paper transport is attempted, but Registration Sensor 2 is not cleared afterward — a fault confirmed via a downstream clearance sensor reading, applicable specifically when a physical paper-transport outcome can be observed. 31-01 is a more fundamental fault: the engine board’s own monitoring of the CL4 engagement command itself — typically via clutch drive current feedback, a dedicated engagement confirmation sensor where fitted, or a mechanical position check — indicates the engagement never completed, independent of whatever the paper subsequently did or did not do
Detection Logic — All platforms:	After WTEN issuance, the engine board commands CL4 to engage. The board monitors for confirmation of successful engagement within a specified timing window — the exact confirmation method (drive current feedback, a dedicated clutch position sensor where fitted, or another engagement-verification method) varies by platform and is documented in the model-specific SM. If engagement confirmation is not received within the window, 31-01 is logged and the print cycle for that sheet is aborted before CL4-driven paper transport is assumed to have occurred
Key Components	Registration clutch (CL4 / CL4A); CL4 drive circuit on the controlling board (BASEB / FRB / EXCB / PFTDB depending on platform); CL4 coil and armature assembly; CL4 mechanical engagement surfaces (clutch disc/plate contact faces); CL4 spring and return mechanism; registration roller shaft and drive coupling (the mechanical load CL4 must overcome to achieve confirmed engagement); CL4 harness and connector
Severity	High — affects every paper source and every print job, since CL4 is shared infrastructure through which every sheet must pass regardless of origin; may be intermittent (occasional engagement failures under specific conditions such as thermal expansion or marginal mechanical wear) before becoming consistent; often the direct escalation point of a CL4 mechanism that has been producing marginal Pattern A behavior (as documented in the 10-04 and 30-01 articles) on specific sources before failing broadly enough to produce 31-01 on all sources
Related Jam Codes	20-01 / 20-02 (vertical transport — for comparison, faults preceding registration arrival), the -40 WTEN codes across all sources (for comparison, faults preceding CL4 commanding), 30-01 (second transfer section — for comparison, a transport fault occurring after successful CL4 engagement), 10-04 (bypass-tray-specific registration clearance fault — for comparison, a downstream-sensor-confirmed variant of a related but distinct failure mode)

All Affected Models and CL4 Component References

Jam Code 31-01 applies to every bizhub model, since the registration clutch is universal infrastructure in the paper path regardless of platform. The CL4 designation, its check code, and its controlling board are consistent with the references already established elsewhere in this series for the registration clutch — this article consolidates them specifically around the clutch engagement fault itself rather than around any single paper source’s journey through the registration area.

bizhub Models	Registration Clutch	CL4 Check Code / Connector	Engagement Confirmation Method	Controlling Board
C250i / C300i / C360i / 250i / 300i / 360i	CL4	CC:21 MC:2, BASEB CN15E-2 (CL4 ON), 3-C	Drive current feedback / mechanical position confirmation — refer to BASEB section of SM for exact method	BASEB
C3350i / C4000i / C4050i	CL4	CC:21 MC:3, BASEB CN22EA-3 (CL4 ON), 12-C	Refer to BASEB section of SM	BASEB
C258 / C308 / C368 / C227 / C287 / C367	CL4	CC:21 MC:2, FRB CN8-7 (CL4_24V), 5-L	Refer to FRB section of SM	MFPB + FRB
368e / 308e	CL4	CC:21 MC:2, FRB CN8-7 (CL4_24V), 5-L	Refer to FRB section of SM	MFPB + FRB
C458 / C558 / C658 / 458e / 558e / 658e	CL4	CC:21 MC:2, FRB CN8-7, 4-K	Refer to FRB / EXCB section of SM	MFPB + FRB + EXCB
C450i / C550i / C650i / 458i / 558i / 658i	CL4	Refer to SM	Refer to SM	MFPB + EXCB + FRB + BASEB
C224e / C284e / C364e / C224 / C284 / C364 / C454 / C554	CL4	Refer to SM (PRCB or MFPB)	Refer to SM	PRCB / MFPB
654e / 754e / 758 / 808 / 958 / PRO 958 / C659 / C759	CL4 or direct-drive equivalent	Refer to SM (PFTDB section)	Refer to PFTDB section of SM	PFTDB + MFPB

CC = Check Code, MC = Multi Code. Confirm the exact engagement confirmation method for the specific model in the SM — this determines exactly what signal or feedback the technician should expect to observe when testing CL4 directly in Service Mode, and affects how a partial-engagement condition is best identified during diagnosis.

ℹ️ 31-01 firing across all sources vs. only under specific load conditions: Before beginning component-level diagnosis, establish whether 31-01 fires uniformly on every print attempt regardless of paper source or media, or whether it correlates with specific conditions — heavier media requiring more registration drive torque, machine warm-up state, or specific times of day correlating with ambient temperature. Uniform failure on every attempt points to a hard clutch or drive circuit fault — proceed directly to Step 3 (coil and drive circuit) and Step 4 (mechanical engagement). Failure correlating with heavier media specifically points to marginal mechanical engagement that has insufficient torque margin for higher-resistance loads — proceed to Step 4 with particular attention to engagement surface wear. Failure correlating with warm-up state or ambient temperature points to a coil winding fault (shorted winding overheating and losing holding force) — proceed to Step 3 with a cold-vs-warm resistance comparison.

Understanding CL4 Engagement — Why 31-01 Occurs

The registration clutch is an electromagnetically-actuated mechanical clutch: when its coil is energized, it draws an armature into contact with a continuously-rotating drive plate, mechanically coupling that rotation to the registration roller shaft and driving the paper forward. When de-energized, a return spring disengages the armature, and the registration roller shaft is free — allowing the roller to sit stationary at the nip while paper forms its loop, without being driven by the continuously-rotating drive plate underneath.

Successful engagement requires several things to happen correctly and in sequence within a very short window: the coil must draw sufficient current to generate an adequate magnetic field; the armature must be mechanically free to move (not seized, not obstructed by debris, not held back by a fatigued or over-tensioned return spring); the armature and drive plate contact surfaces must have sufficient friction to transmit rotational force once they meet (not glazed, not contaminated, not worn smooth); and this entire sequence must complete within the timing window the engine board is monitoring. A failure at any point in this chain prevents confirmed engagement and produces 31-01.

Five root cause categories produce 31-01, ordered by frequency in field-installed bizhub machines:

• Category 1 — CL4 mechanical engagement surface wear (dominant cause on higher-cycle machines): The clutch disc and armature contact faces — the friction surfaces that transmit rotational force once the armature is drawn into contact — have worn smooth or glazed from repeated engagement cycles over the clutch’s service life. A worn engagement surface may still allow the armature to be drawn into contact by the coil’s magnetic field, but the resulting friction is insufficient to reliably transmit full rotational force to the registration roller shaft, particularly under the higher resistance load of heavier paper. This produces the correlation-with-heavy-media pattern described in the notice above, and it is the most common cause of 31-01 on machines that have accumulated a significant clutch cycle count without a corresponding CL4 replacement. Because the clutch disc assembly is generally a sealed, non-serviceable-at-the-surface component, this category is resolved by full CL4 replacement rather than by any cleaning or adjustment procedure
• Category 2 — CL4 return spring fatigue or mechanical binding: A fatigued or damaged return spring can either fail to fully release the armature between cycles (leaving it in a partially-engaged resting state that interferes with clean re-engagement on the next command) or, in cases of spring damage or debris intrusion, can physically obstruct the armature’s travel toward the drive plate when engagement is commanded. Both conditions prevent the clean, complete engagement motion the engine board’s monitoring expects to see within the timing window. This category is confirmed by physical inspection of the armature’s freedom of movement and the spring’s condition when CL4 is accessed
• Category 3 — CL4 coil winding fault (open or shorted winding): An open-circuit coil winding cannot generate any magnetic field at all, producing complete and consistent engagement failure on every cycle — the most severe and most straightforward-to-diagnose variant of this fault, confirmed immediately by a coil resistance measurement showing infinite resistance. A shorted winding, by contrast, may still generate a magnetic field sufficient for engagement under some conditions but draws excess current and can overheat during sustained operation, producing the warm-up-correlated failure pattern described in the notice above — confirmed by a coil resistance measurement below the SM-specified value, and further confirmed by comparing resistance measured cold versus after a period of normal machine operation
• Category 4 — CL4 drive circuit fault on the controlling board: The coil itself tests correctly at the expected resistance, but the drive transistor or associated circuitry on the controlling board (BASEB / FRB / EXCB / PFTDB depending on platform) that supplies the commanded engagement current has failed, is supplying insufficient current, or is not responding to the engagement command at all. This category is distinguished from Category 3 by directly measuring voltage/current at the CL4 connector during a commanded Service Mode engagement test — a healthy coil with no drive signal present at the connector confirms the fault is upstream on the controlling board rather than in the clutch itself
• Category 5 — Foreign object or debris preventing armature travel: Debris — paper dust, toner, or in rare cases a small foreign fragment — has entered the clutch mechanism’s housing and is physically obstructing the armature’s travel path, preventing it from fully seating against the drive plate even when the coil correctly energizes. This category is confirmed by physical inspection once the clutch is accessed, and is more common on machines operating in dustier environments or on machines significantly overdue for PM service in the registration area

Step 1 — Clear the Paper and Confirm the Stop Position

Because 31-01 fires at the point of CL4 commanding — before any paper transport driven by that engagement is assumed to have occurred — the paper stop position for this code is generally straightforward and confirms the code’s classification rather than providing extensive differential diagnostic detail on its own.

1. Open the right-side cover or registration area access panel as indicated by the operator panel jam indicator
2. Locate the paper: it should be found at the registration nip, flat and undamaged, in the loop-formed position it reached before CL4 was commanded — since CL4’s engagement was never confirmed, the registration rollers should not have driven the paper any further forward from where it arrived
3. Remove the paper carefully. Its clean, undamaged condition — distinct from the crumpled condition documented for 20-02, and distinct from the “confirmed partially advanced” condition documented for 30-01’s Pattern B — confirms the paper’s own transport was never attempted by CL4 in the first place, consistent with 31-01’s definition
4. If the paper is instead found partially advanced or in an unexpected position, reconsider whether 31-01 is genuinely the correct classification for this event rather than a related but distinct code — confirm the exact code displayed against the SM before proceeding, since a partially-advanced paper is more consistent with a fault occurring after some degree of CL4 engagement was achieved

Step 2 — Review Service History and Establish the Failure Pattern

1. Access the Error History log in Service Mode and review recent 31-01 events for consistency and correlation, using the diagnostic split established in the notice above (uniform vs. media-correlated vs. thermal-correlated) to direct the investigation efficiently
2. Check whether 31-01 has been preceded by a documented history of Pattern A behavior on 10-04 (bypass tray) or 30-01 (general sources) events — marginal CL4 engagement that was sufficient to pass on lighter media or under favorable conditions but has now degraded to the point of failing the engine board’s own engagement confirmation check consistently. This escalation pattern, where a marginal mechanism-level fault first appears as an occasional downstream symptom before becoming severe enough to trigger its own dedicated fault code, is common for wear-based clutch failures
3. Check the total copy counter and any CL4-specific service history against the clutch’s rated service life or PM replacement interval as specified in the model SM
4. Check for any recent service intervention in the registration area — CL4 replacement, registration roller service, or any work requiring the registration assembly to be accessed — that might correlate with the fault’s onset if it is a new-issue rather than a wear-progression pattern

Step 3 — Test CL4 Coil and Drive Circuit

1. With the machine powered off and the CL4 harness accessible, measure coil resistance at the connector using a multimeter, comparing the result against the SM-specified value:
   • Infinite resistance (open circuit): coil winding has failed. Replace CL4
   • Resistance significantly below specification: shorted winding. Replace CL4. If the failure pattern established in Step 2 correlated with warm-up/thermal conditions, repeat this measurement after 30 minutes of normal machine operation to directly confirm the thermal degradation pattern before replacement, documenting both readings in the service log
   • Resistance within specification: coil is electrically healthy. Proceed to test the drive circuit and mechanical engagement
2. With the coil confirmed healthy, power the machine on and, in Service Mode, command CL4 to engage using the check code from the component table. With an appropriate meter connected at the CL4 connector (per safe practice for the specific test being performed), verify that drive voltage/current is actually present at the connector during the commanded engagement window:
   • No drive signal present despite a healthy coil: the fault is in the controlling board’s drive circuit (Category 4). This requires board-level service per the model SM — confirm all connectors between the board and CL4 are correctly seated before concluding the board itself has failed, since a harness fault can also produce this symptom and is a lower-cost fix
   • Drive signal is present and appears correct: the fault is mechanical rather than electrical. Proceed to Step 4

Step 4 — Inspect CL4 Mechanical Engagement

1. With the coil and drive circuit confirmed electrically healthy, access the CL4 assembly per the model SM and visually/manually inspect the mechanism:
   • Manually move the armature through its range of travel (with power off) and confirm it moves freely with no binding, and that the return spring returns it promptly and completely to the disengaged position. Resistance, binding, or incomplete return indicates Category 2 (spring fatigue or mechanical binding)
   • Inspect the clutch disc and armature contact faces for glazing, wear, or a polished/shiny appearance distinct from a fresh friction surface. This is generally only fully visible if the clutch assembly can be at least partially disassembled per the SM’s documented procedure — do not attempt disassembly beyond what the SM specifically documents, as clutch assemblies are frequently serviced as a complete unit rather than at the component level
   • Inspect for visible debris or foreign material in the clutch housing that could be obstructing armature travel (Category 5). Clean per the SM’s guidance if found, using only the cleaning method and materials the SM specifies for this component — inappropriate cleaning agents can degrade the friction surface further
2. With the machine powered on, command CL4 to engage in Service Mode and directly observe/listen to the mechanism (where safely observable per the SM’s access guidance):
   • A healthy engagement produces a firm, immediate, and consistent click on every commanded cycle. Attempt to turn the registration roller shaft by hand during a commanded engagement — it should be firmly locked, difficult or impossible to turn against the engaged clutch
   • A registration roller shaft that can still be turned with moderate hand force during a commanded engagement confirms insufficient torque transmission — Category 1 (worn engagement surfaces) if the coil and drive circuit have already tested healthy
   • Repeat the command several times in rapid succession — inconsistent engagement (firm on some cycles, weak or absent on others) with electrically healthy coil and drive circuit further confirms mechanical wear or intermittent binding as the cause
3. Based on the findings: replace CL4 as a complete assembly if mechanical wear (Category 1) or spring/binding issues (Category 2) beyond simple cleaning are confirmed; clean and retest if debris obstruction (Category 5) is the sole finding and mechanical inspection is otherwise clean. After any CL4 replacement, confirm correct installation orientation per the SM — registration clutches on most bizhub models have a specific rotational/directional installation requirement, and incorrect installation produces immediate engagement failure indistinguishable in symptom from the original fault

Step 5 — Confirm Repair and Verify Across Media Types

1. After any repair action (CL4 replacement, drive circuit repair, harness reseating, or debris cleaning), run a test sequence covering: standard plain paper from at least two different sources, and — if the original failure pattern correlated with heavier media — a heavier stock sample as well, to confirm the repair holds under the load condition that originally revealed the fault
2. If the original failure pattern correlated with thermal/warm-up conditions, run the test sequence again after 30 minutes of continuous operation to confirm the repair holds under warm operating conditions, not just at a cold start
3. Monitor over an extended print run (100+ sheets across the affected sources/media) before considering the repair complete, given that intermittent clutch engagement issues can sometimes appear to resolve immediately after a repair only to recur under sustained operation

Quick Reference — Troubleshooting by Symptom

Symptom	Most Likely Cause	First Action
31-01 on every print attempt, every source, every media type; paper found clean and undamaged at registration nip	Hard CL4 fault — open/shorted coil, failed drive circuit, or severely worn/seized mechanical engagement	Measure CL4 coil resistance against SM specification; if healthy, verify drive signal presence at connector during commanded engagement; if drive signal present, inspect mechanical engagement directly
31-01 correlated specifically with heavier or coated paper stock; standard plain paper unaffected	CL4 mechanical engagement surface wear — insufficient torque margin for higher-resistance loads	Confirm coil and drive circuit are electrically healthy first; inspect and test mechanical engagement per Step 4; replace CL4 if worn engagement surfaces are confirmed or strongly indicated by torque testing
31-01 correlated with machine warm-up time or ambient temperature; clears when machine is cold, appears after sustained operation	CL4 coil with a shorted winding, overheating and losing holding force at operating temperature	Measure coil resistance cold and again after 30 minutes of operation; replace CL4 if resistance is below specification or drops significantly with temperature
31-01 intermittent, inconsistent engagement on repeated Service Mode commands with coil and drive circuit confirmed healthy	Mechanical binding, spring fatigue, or early-stage engagement surface wear	Manually inspect armature travel and return spring condition; inspect for debris; replace CL4 if binding or spring fatigue is confirmed beyond simple cleaning
31-01 with coil testing at correct resistance but no drive signal present at the connector during a commanded Service Mode engagement	Controlling board drive circuit fault, or a harness/connector fault between the board and CL4	Reseat all connectors in the CL4 signal path first; if drive signal remains absent, this is a board-level fault requiring service per the model SM
31-01 appeared immediately after a documented history of occasional Pattern A behavior on 10-04 or 30-01 events	Progressive CL4 wear that has now crossed the threshold from occasional marginal engagement to consistent engagement-confirmation failure	Treat as confirmed CL4 wear; proceed directly to mechanical engagement inspection and replacement per Step 4 rather than re-testing electrical components extensively
31-01 immediately after CL4 replacement	Incorrect installation orientation, connector not fully reseated, or a defective replacement part	Verify installation orientation against SM; confirm harness connector fully seated; retest with a different replacement unit if the fault persists with correct installation confirmed

Understanding the 31-xx Registration Section Jam Code Family

Jam Code 31-01 belongs to the 31-xx registration section code family, scoped specifically to the registration clutch (CL4) engagement event itself, positioned precisely between the WTEN authorization codes and the second transfer section transport codes in the overall print cycle sequence:

• 31-01 — Registration clutch engagement failure — CL4 was commanded to engage following WTEN issuance, but confirmed engagement was not achieved within the timing window. A mechanism-level fault in the clutch itself, its drive circuit, or its mechanical engagement components — not a transport fault and not a board-communication fault. This article

This code family sits at a precise, narrow point in the overall print cycle: everything upstream (source feed, vertical transport, registration arrival, loop forming, WTEN handshake) is confirmed successful by the time 31-01 can fire, and everything downstream (paper transport toward the second transfer section) has not yet been attempted because CL4’s own engagement was never confirmed. This makes 31-01 diagnostically unambiguous in scope compared to codes that describe transport-timing outcomes across a physical distance — the entire investigation is contained within the CL4 mechanism and its immediate drive circuit.

Preventing Jam Code 31-01 From Recurring

• Track CL4 engagement cycle count against its rated service life where the model SM specifies one, and replace proactively rather than waiting for consistent 31-01 failure. Because CL4 is shared infrastructure processing every single sheet through the machine regardless of source, its cycle count accumulates faster than almost any other single component in the paper path, and proactive replacement at the specified interval prevents the wear-progression pattern from ever reaching customer-visible failure
• Treat any documented history of Pattern A behavior on 10-04 or 30-01 events as an early warning for CL4 wear, and inspect the clutch proactively rather than waiting for it to escalate to 31-01. Because marginal CL4 engagement can appear first as an occasional, media-specific downstream symptom before crossing the threshold into a consistent engagement-confirmation failure, recognizing this escalation pattern in the service log allows CL4 replacement to be scheduled proactively during a routine visit rather than as an emergency callback
• Include CL4 mechanical inspection — armature travel, return spring condition, and audible engagement quality — in PM visits on high-volume machines, even without a specific reported fault, given the component’s universal exposure to every print cycle
• Keep the registration area free of paper dust and debris accumulation through regular PM cleaning, reducing the likelihood of Category 5 (debris obstruction) contributing to engagement failures
• Document CL4 replacement with the copy counter value at replacement in the service log, allowing any future technician to immediately assess whether the clutch is within its expected service life when investigating a related fault

Professional Technician Summary

Jam Code 31-01 is the registration clutch engagement failure — CL4 was commanded to engage following successful WTEN authorization, but the engine board’s own monitoring did not confirm successful engagement within the timing window. This is the narrowest and most upstream fault in the registration-area code family: everything before this point in the print cycle (feed, transport, registration arrival, loop forming, WTEN) is confirmed successful, and everything after it (paper transport toward the second transfer section) has not yet been attempted.

The diagnostic scope for 31-01 is contained entirely within the CL4 clutch, its drive circuit, and its mechanical engagement components. No transport hardware, no firmware or board-communication system, and no downstream sensor is implicated. A technician should move directly to coil resistance testing, drive circuit signal verification, and mechanical engagement inspection — in that order — without investigating any of the systems that produce the codes documented elsewhere in this series for upstream or downstream faults.

The failure correlation pattern — uniform, media-specific, or thermal — determines the most efficient diagnostic order. A uniform failure on every attempt points to a hard electrical or severely worn mechanical fault and is generally straightforward to confirm with coil resistance and drive signal testing. A media-specific correlation with heavier stock points to marginal mechanical engagement surface wear with insufficient torque margin. A thermal/warm-up correlation points specifically to a shorted coil winding and is confirmed by comparing cold and warm resistance measurements.

31-01 is frequently the escalation point of a CL4 that has already been producing marginal, media-specific symptoms under the guise of other codes — most notably the Pattern A behavior documented for 10-04 and 30-01 elsewhere in this series. Recognizing this progression in a machine’s service history allows CL4 wear to be identified and addressed before it reaches the point of a full, all-sources 31-01 failure.