BCU 523921.05 – E11/2 /E31R Worklights on Rear of Roof On, No Current Present. John Deere System Advisory.

BCU 523921.05 (BCU )

Code: 523921.05



Diagnostic trouble code BCU 523921.05 is triggered when the power module PC0 measures a current of less than 500 mA in lead 1087, even though the worklights on the rear of the roof (E11/2 or E31R) are switched on. This condition indicates an open circuit, suggesting a break or disconnection in the electrical pathway that should be supplying power to these lights.


The system may prevent the rear roof worklights from operating due to the lack of current, potentially affecting visibility and safety 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 1087 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 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 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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