BCU 523920.05 – Outer Worklights on Front of Roof On, No Current Present. John Deere System Advisory.

BCU 523920.05 (BCU )

Code: 523920.05



Diagnostic trouble code BCU 523920.05 is triggered when the power module PC0 measures a current of less than 500 mA in lead 1047, while the outer worklights on the front of the roof (E18/2) are activated. This condition typically indicates an open circuit, suggesting a break or disconnection in the electrical pathway that should be powering these worklights.


The system may prevent the outer worklights from operating due to the lack of current, which could affect visibility if these lights are required for operation. An alert may be displayed to inform the operator of the electrical issue, prompting immediate troubleshooting.


  • Inspect Wiring and Connections: Examine all wiring and connections related to lead 1047 for any signs of breaks, disconnections, or wear that could result in an open circuit.
  • Test for Continuity: Use a multimeter to check for continuity in the circuit. This will help identify the location and nature of the open circuit.
  • Repair or Replace Faulty Wiring: If a break or disconnection is found, repair or replace the affected wiring to restore proper electrical flow.
  • Check Light Fixture Integrity: Ensure that the outer worklights themselves are not faulty. Test the lights for operational integrity and replace them if necessary.
  • Reset the System and Test: After addressing the electrical issues, reset any fault codes and test the system to ensure the outer worklights are operational and receiving the correct current when activated.


Regular and thorough maintenance of the electrical systems, particularly for critical components like lighting, is crucial for ensuring reliable machinery operation. Proactive management of these systems helps avoid operational downtime and ensures the equipment functions safely and efficiently. Addressing open circuit issues promptly is essential to maintaining the operational readiness and effectiveness of the lighting system.

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