“TOP OF FORM FAULT” – Datamax-O’neil M-Class Error Message Article


This Error Message Article explains the Datamax-O’neil M-Class Mark II error message “TOP OF FORM FAULT” that can appear on the printer LCD display and details how to fix the underlying problem that caused it to appear.


Assuming that there is no mechanical problem with the printer, the error message indicates that there is a mismatch between the media sensor type and media (label) installed on the printer.


  1. Printer (hardware) Settings

    1. Label media generally comes in one of three styles. Different brand may have slightly different terminology for them.
      1. Continuous – There are no visible spaces between each labels
      2. Mark (Reflective) – There is a black mark or line on the back side of the label liner. This mark may only be on the side or covers the entire width of the label
      3. GAP (DieCut)- There is a uniform gap between labels.
    2. The Mark II printer has 3 different settings for Sensor Type:
      1. CONT – for Continuous labels
      2. REFL – for Mark style labels
      3. EDGE – for GAP style labels
    3. Make sure that the sensor type setting on the printer matches the type of labels.
  2. Calibrate the printer

    1. Ensure that the printer is ON and in an idle state (i.e., not off-line) with media loaded, the media sensor adjusted, and the sensor type selected.Press and hold the FEED Key until one label has been output then release the key and wait for the printer to process the data.
    2. CALIBRATION COMPLETE – will be displayed, and the media will be advanced to the next top of form if calibration was successful
  3. Software Settings

    1. CODESOFT: From menu bar: File / Label/Page Setup / Label
    2. LABELVIEW: From menu bar: File / Label/Page Setup / Label tab
  4. Printer Driver Settings

    1. This option requires you to look into the settings for the printer driver. Depending on the author, the feature you need to check can be buried deep within the driver properties.  For example;
      1. Datamax-O’neil A-4408 Mark II printer – written by Seagull Scientific
        1. In Printer Properties
          1. Select Tools / Configure / Configure Printer
          2. Select proper Sensor Type
      2. Datamax-Oneil M-4308 Mark II printer – written by Teklyxn
        1. In Printer Properties
        2. In General tab / expand Advanced






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