BCU 523920.12 – Outer Worklights on Front of Roof Off, Current Detected. John Deere System Advisory.

BCU 523920.12 (BCU )

Code: 523920.12



Diagnostic trouble code BCU 523920.12 is activated when the power module PC0 detects a current exceeding 1 amp in lead 1047, despite the outer worklights on the front of the roof (E18/2) being switched off. This unexpected current flow typically indicates a short in the circuit or an internal fault within the power module, which could potentially lead to overheating, damage to electrical components, and an increased risk of fire.


The system likely initiates overload protection to shut down the affected circuit and prevent further damage. An alert may be issued to the operator through diagnostic indicators or warning messages, signaling the need for immediate maintenance.


  • Inspect Wiring and Connectors: Thoroughly examine the wiring and connectors associated with lead 1047 for any signs of damage such as worn insulation, exposed wires, or other abnormalities that might cause a short circuit.
  • Test for Short to Ground: Use a multimeter to test the circuit for continuity and to locate any potential short to ground. Focus on identifying the specific locations where shorting may occur.
  • Replace or Repair Damaged Components: If specific areas of damage or malfunction are identified, replace or repair the faulty wiring or components to resolve the short circuit issue.
  • Check Power Module Integrity: Ensure that the power module PC0 itself is not the source of the fault. If the module is damaged, it may require testing or replacement.
  • Reset and Test the System: After repairs are made, reset any associated fault codes and test the system to ensure that the issue has been resolved and that the current remains within safe operational limits.


Regular maintenance and proactive checks of the vehicle’s electrical systems are crucial for identifying and rectifying issues such as shorts and unexpected current conditions. Early detection and correction of electrical faults help maintain the safety and efficiency of operations, thereby extending the life of the equipment. Addressing such issues promptly is key to minimizing downtime and ensuring that the lighting system remains operational and effective.

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