Konica Minolta C368 1201 False Paper Jam: PS21 Sensor Troubleshooting

Key Takeaways

• The Konica Minolta bizhub C368 may display a 1201 paper jam even when all sheets appear to have successfully passed through the machine.
• In the service case described in this article, the machine continued to detect paper in Tray 2 even when the tray was empty.
• Replacing the Tray 2 feed clutch CL5 did not resolve the problem.
• The decisive diagnostic evidence came from Service Mode I/O monitoring, where the PS21 signal remained at 0 even when the sensor actuator was manually operated.
• This localized the fault to the Tray 2 paper-out detection circuit, rather than the feed clutch.
• In this case, replacing the PS21 paper-out sensor assembly resolved the problem.

Fault Scenario: Printing Completes, Yet the Machine Reports a 1201 Jam

A Konica Minolta bizhub C368 was experiencing an unusual 1201 paper jam during batch printing from Tray 2.

The key symptoms were:

• All sheets appeared to exit the machine normally.
• No paper fragments or obstructions were found in the paper path.
• The machine did not display an out-of-paper condition when Tray 2 was empty.
• After the final sheet exited, the control panel displayed 1201 Paper Jam, associated with Channel 2.
• The Tray 2 feed clutch CL5 had already been replaced, but the problem remained.

This combination of symptoms suggested that the problem was not simply a mechanical paper-feed failure.

The decisive step was to compare the sensor signals using Service Mode I/O monitoring.

Why the PS21 I/O Signal Was the Key Diagnostic Evidence

Normal Tray 1 Behavior

The Tray 1 sensor changed state normally when the sensor actuator was moved.

Abnormal Tray 2 Behavior

For Tray 2, manually operating the paper-out sensor actuator produced no change:

This was the key diagnostic finding.

Because the PS21 signal remained at 0 regardless of the sensor actuator position, the machine continued to interpret Tray 2 as containing paper.

What Does the Konica Minolta C368 1201 Error Mean?

Paper Feed and Vertical Transport Detection

The 1201 jam condition in this case is associated with the paper feed and vertical transport detection sequence.

The relevant sensors include:

• PS20 — Tray 2 feed detection
• PS19 — vertical transport detection
• PS21 — Tray 2 paper-out detection

The important point is that the machine does not determine a paper jam simply by detecting physical paper in the machine. It evaluates whether the expected sensor signals occur within the required sequence and timing.

How the 1201 Timing Error Occurs in This Case

In this service case, the 1201 error was ultimately traced to an abnormal PS21 paper-out sensor signal. Because PS21 remained at 0, the machine continued to interpret Tray 2 as containing paper and maintained an incorrect paper-present status.

After the final sheet had exited, the machine still expected another feed cycle.

When the expected sensor sequence did not occur within the required timing window, the controller reported the 1201 paper jam.

Step-by-Step Troubleshooting Workflow

1. Inspect the Tray 2 Mechanical Linkage

First, completely remove Tray 2 and inspect the paper-out detection mechanism.

Check for:

• Paper scraps
• Toner or dust accumulation
• A sticking linkage lever
• Weak or damaged springs
• Broken mechanical parts
• Incorrect alignment of the rear linkage bracket

Manually move the sensor actuator several times.

It should move freely and return to its original position when released.

If the mechanical actuator moves correctly but the I/O signal does not change, continue to the electrical checks.

2. Check the PS21 Optical Sensor

Power off the machine before accessing the sensor area.

Inspect the PS21 optical sensor window for contamination.

If necessary, clean the optical surfaces using an appropriate lint-free cleaning material and allow the area to dry before testing.

After cleaning, enter the appropriate I/O monitoring mode and operate the actuator manually.

If the signal changes: the optical detection system may have been affected by contamination.

If the signal remains fixed at 0: continue with wiring and sensor testing.

3. Inspect the PS21 Wiring Harness

Repeated insertion and removal of the paper tray can place mechanical stress on the wiring harness and connector.

Inspect for:

• Damaged insulation
• Broken conductors
• Loose connector pins
• Oxidized contacts
• Poor connector engagement
• Possible short circuits

Reconnect the harness securely and repeat the I/O test.

4. Determine Whether the Sensor Assembly Has Failed

If:

1. the mechanical actuator moves correctly,
2. the optical path is clean,
3. the wiring and connectors are properly connected, and
4. PS21 remains at 0 regardless of actuator position,

then the sensor assembly itself becomes the primary suspect in this case.

The sensor’s internal photoelectric circuit may have failed, preventing the I/O signal from responding correctly to the actuator position.

The recommended repair in the documented case was to replace the Tray 2 paper-out sensor (PS21) assembly.

When Should You Check the FRB Control Board?

The FRB control board should not be the first component to replace when only the PS21 signal is abnormal.

If PS19, PS20, and PS21 all show abnormal behavior, or if multiple Tray 2 sensor circuits are affected, further investigation of the FRB control board and related circuitry may be necessary.

However, when:

• PS19 operates normally,
• PS20 operates normally,
• only PS21 remains fixed at 0,

the troubleshooting should remain focused on the PS21 sensor circuit and its wiring before considering a board-level failure.

Repair Verification After Replacing PS21

I/O Monitor Verification

After replacing the PS21 sensor assembly:

Tray 2 empty:

• PS21 = 1
• Out-of-paper indication should appear.

Tray 2 loaded:

• PS21 = 0
• Out-of-paper indication should turn off.

The signal should change immediately when the sensor actuator is operated.

Continuous Paper Feed Test

Perform a batch printing test from Tray 2.

The machine should:

• Feed all sheets normally.
• Stop after the paper supply is exhausted.
• Display the appropriate out-of-paper condition.
• No longer generate the 1201 false jam at the end of the job.

PS19 Vertical Transport Sensor Verification

Also confirm that PS19 responds correctly during paper transport.

The actuator should move freely and the I/O signal should change in accordance with the paper path sequence.

Common Repair Mistakes to Avoid

FAQ: Frequently Asked Questions

What does error 1201 mean on a Konica Minolta C368?

Error 1201 indicates a paper-feed or transport timing problem in the relevant paper path. In the service case described here, the error was ultimately associated with an abnormal PS21 paper-out sensor signal.

Why does the C368 show 1201 after the last sheet exits?

In this case, the machine continued to interpret Tray 2 as containing paper because the PS21 signal remained at 0. After the final sheet exited, the expected feed and sensor sequence was no longer completed, resulting in the 1201 error.

Can the CL5 feed clutch cause a 1201 error?

A feed clutch can contribute to paper-feed problems, but replacing CL5 does not correct an incorrect paper-detection signal. In this documented case, CL5 replacement did not resolve the fault because the problem was traced to PS21.

What does PS21 do on the C368?

PS21 is the Tray 2 paper-out detection sensor in the troubleshooting case described here. Its signal tells the machine whether paper remains available in the tray.

How can Service Mode I/O help diagnose a C368 paper jam?

I/O monitoring allows technicians to observe whether a sensor changes state when its actuator is physically operated. This can help distinguish a mechanical paper-feed problem from a sensor, wiring, or control-circuit problem.

Conclusion

A Konica Minolta bizhub C368 1201 paper jam does not always mean that there is a physical sheet stuck in the paper path.

In this documented service case, all paper successfully exited the machine, but the C368 continued to detect paper in Tray 2 because the PS21 paper-out sensor signal remained at 0.

Replacing the CL5 feed clutch did not resolve the problem because the fault was not caused by insufficient feed drive.

The decisive diagnostic step was Service Mode I/O monitoring, which showed that PS21 did not respond to manual actuator movement.

The repair was to replace the PS21 paper-out sensor assembly, followed by I/O verification and a continuous paper-feed test.

Practical rule: When a Konica Minolta C368 reports a 1201 jam even though the paper path is clear, check the relevant sensor states before replacing mechanical drive components.