BCU 523921.01 – E11/2 /E31R Worklights on Rear of Roof, Power Supply Fault. John Deere System Advisory.

BCU 523921.01 (BCU )

Code: 523921.01



Diagnostic trouble code BCU 523921.01 is triggered when the power module PC0 measures a supply voltage of less than 3 volts at lead 0782 while the worklights on the rear of the roof (E11/2 /E31R) are activated. This low voltage reading suggests a power supply fault in the circuit, potentially due to inadequate wiring, poor connections, or a malfunction within the power module itself. Insufficient voltage can prevent the worklights from operating effectively, impacting visibility and safety.


The system may disable the worklights to prevent damage or operational inefficiency due to the low voltage. An alert may be displayed to inform the operator of the power supply issue, prompting immediate troubleshooting.


  • Inspect Wiring and Connections: Check the wiring and electrical connections for lead 0782. Look for signs of damage, wear, or loose connections that could be causing the voltage drop.
  • Measure and Verify Voltage Levels: Use a multimeter to check the voltage at the output for the worklights during operation to confirm the low voltage condition.
  • Check Power Module Functionality: Ensure that the power module PC0 is functioning correctly and providing the necessary voltage to all outputs. If the module is faulty, it may need to be repaired or replaced.
  • Replace or Repair Faulty Components: If any components, including wiring or connectors, are found to be defective, replace or repair them to ensure proper voltage supply to the worklights.
  • Reset the System and Test: After making the necessary repairs, reset the electrical system to clear any fault codes and test the worklights to ensure they are receiving the correct voltage and functioning properly.


Regular maintenance and inspection of electrical systems are crucial for the safe and effective operation of worklights and other electrical components on agricultural machinery. Addressing electrical issues promptly helps to maintain optimal visibility and safety conditions, ensuring that all systems function as expected under all operating circumstances.

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