JDL 000629.12 – Control Unit Internal Fault

JDL 000629.12 (JDL 629.12)

Code: 000629.12

Shortcode: 629.12


This diagnostic trouble code, JDL 000629.12, is triggered when an electronic malfunction is detected within the control unit. This fault indicates that the control unit has identified an internal error that affects its ability to operate correctly.


When this error code is triggered, the equipment may experience reduced functionality or complete shutdown of the affected systems. The control unit may attempt to enter a safe mode to prevent further damage or malfunction.


Inspect Control Unit:

  • Perform a visual inspection of the control unit for any obvious signs of damage, such as burnt components, loose connections, or corrosion.
  • Ensure all connectors are properly seated and free of debris.

Update Control Unit Software:

  • Verify that the control unit software is up-to-date. Install any available updates to address known issues and improve system stability.

Perform a Hard Reset:

  • Disconnect the power supply to the control unit for a few minutes and then reconnect it. This can sometimes clear temporary faults.

Consult Technical Support:

  • If the issue persists after performing the above steps, consult the manufacturer’s technical support for further assistance.
  • Provide the diagnostic trouble code and any relevant information gathered during the inspection.

Replace Control Unit (if necessary):

  • If the control unit is determined to be faulty and cannot be repaired, replacement may be necessary to restore full functionality.


Internal faults within the control unit can sometimes be indicative of deeper issues, such as voltage irregularities or environmental factors (e.g., extreme temperatures, moisture ingress). It is important to ensure that the operating environment is within the specified parameters for the equipment. Regular maintenance and inspection can help prevent such faults from occurring.

Control Units: John Deere

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