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Error code reference

Samsung Multifunction Printer Error Code #04-000

LSU motor does not operate (Polygon Motor Error).

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LSU motor does not operate (Polygon Motor Error).

First step from the service manual

After checking the LSU motor rotation noise, check the motor signal.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What #04-000 means on a Samsung multifunction printer

The Samsung #04-000 error code indicates a Polygon Motor Error, meaning the LSU (Laser Scanning Unit) motor has failed to operate correctly or has not reached its required rotational speed. The LSU contains a polygon mirror motor, a high-speed spinning component responsible for deflecting the laser beam across the photosensitive drum to form the latent image during printing. When this motor fails to start, stalls, or does not reach its target RPM within the expected startup window, the printer halts and generates this error to prevent incomplete or distorted print output.

The polygon motor is a brushless DC motor that receives drive signals from the main control board. The printer firmware monitors a feedback signal (often called the FG or frequency generator signal) to confirm the motor has reached proper operating speed. If this feedback signal is absent, irregular, or out of range, the controller interprets it as a motor failure and triggers the #04-000 code. Common root causes include a seized or mechanically obstructed polygon motor, a failed motor driver circuit on the main board, or a broken or disconnected signal harness between the LSU assembly and the control board.

Diagnosis begins by listening for polygon motor rotation noise immediately after a print job is initiated. A functioning motor produces a distinct high-pitched whine or hum as it spins up. If no rotation noise is present, the motor itself or its drive circuit is suspect. If rotation noise is present but the error still triggers, the issue likely lies with the motor feedback signal path, including the connector, wiring harness, or the signal-reading circuitry on the main board. The LSU assembly is typically replaced as a complete unit rather than repairing the motor in isolation.

Source: manufacturer service documentation.

Common causes of #04-000

  1. 01

    Failed or seized polygon motor

    Part replacement

    The polygon mirror motor inside the LSU assembly has mechanically failed or seized, preventing it from spinning. Listen for the absence of a high-pitched spin-up noise when a print job starts as a key indicator.

  2. 02

    Disconnected or damaged LSU wiring harness

    Wiring / connection

    The connector or wiring harness carrying the motor drive and feedback signals between the LSU and the main control board may be loose, corroded, or broken. Inspect all connectors at the LSU assembly and trace the harness for visible damage.

  3. 03

    Failed motor driver circuit on the main control board

    Part replacement

    If the main board's motor driver section has failed, it will not deliver the correct drive voltage to spin up the polygon motor. This is suspected when the harness and LSU assembly both test as intact but the motor still does not receive a drive signal.

  4. 04

    Faulty motor feedback signal

    Part replacement

    The polygon motor may spin but fail to send a valid FG (frequency generator) feedback signal back to the control board, causing the printer to register a motor error even though mechanical rotation is occurring. This points to a fault within the LSU assembly itself.

  5. 05

    Contaminated or obstructed LSU assembly

    Wiring / connection

    Dust, debris, or foreign material lodged in the LSU can physically impede the polygon motor from reaching speed. Inspect the LSU for any visible contamination around the motor area.

See the test procedure for each cause

Frequently asked questions about #04-000

What does #04-000 mean on a Samsung multifunction_printer?
The #04-000 error indicates a Polygon Motor Error, meaning the LSU (Laser Scanning Unit) motor has failed to operate or reach its required rotational speed. This motor drives the spinning polygon mirror that deflects the laser beam to form print images. The printer stops all operation when this error is detected to prevent damaged output or internal harm. The LSU assembly or its signal circuit must be inspected to resolve it.
Can I fix the #04-000 error myself on a Samsung printer?
Some basic checks are within reach of a knowledgeable DIYer, such as inspecting and reseating the wiring harness connectors leading to the LSU assembly. However, if the polygon motor itself has failed or the motor driver circuit on the main board is faulty, replacing the LSU assembly or the main board is required, and these repairs are best handled by a technician familiar with laser printer internals. Attempting to open the LSU assembly itself is not recommended, as it is a sealed optical unit.
Will resetting the printer clear the #04-000 error?
A power cycle or reset may temporarily clear the error display, but if the underlying polygon motor fault is still present, the error will return as soon as the printer attempts its next print job. A reset alone does not repair a failed motor, a broken harness, or a faulty control board circuit. The root cause must be addressed for the printer to return to normal operation.
Is it safe to continue using my Samsung printer when the #04-000 error appears?
The printer will not allow normal printing while this error is active, which prevents unsafe or incomplete operation. You should not attempt to bypass or force the printer to operate while this fault is present. Leave the printer powered down until the LSU motor fault has been diagnosed and repaired.
How much does it cost to repair a Samsung printer with error #04-000?
Repair costs vary depending on the failed component. If the fix is a reseated or replaced wiring harness, costs may be relatively low, generally in the range of $20 to $80 for parts and labor. Replacing the full LSU assembly typically costs between $80 and $200 depending on the printer model and parts availability. If the main control board's motor driver circuit has failed and a board replacement is needed, costs can range from $150 to $350 or more, at which point evaluating repair versus replacement of the printer may be worthwhile.

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