PLC 000629.12 – Control Unit Internal Fault

PLC 000629.12 (PLC 629.12)

Code: 000629.12

Shortcode: 629.12


This diagnostic trouble code (DTC) is triggered when an electronic malfunction is detected within the control unit. This could involve issues with the internal circuits, memory, or processor of the control unit.


When this code is detected, the equipment may enter a safe mode to prevent damage or further malfunction. Certain functions controlled by the affected unit might be limited or disabled until the fault is resolved.


  • Inspect Control Unit:
    • Examine the control unit for any visible signs of damage or loose connections. Ensure all connectors are securely attached.
  • Reset the Control Unit:
    • Perform a power cycle by turning off the machine, waiting for a few minutes, and then restarting it to see if the error clears.
  • Update Firmware:
    • Check if there is a firmware update available for the control unit. Updating the firmware can resolve known issues.
  • Replace Control Unit:
    • If the problem persists after a reset and firmware update, consider replacing the control unit.


Internal faults in the control unit can be symptomatic of deeper issues. Regular maintenance and timely software updates are crucial to prevent such malfunctions.

Control Units: John Deere

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