BCU 523691.05 – Lower Worklights on Cab Frame On, No Current Present at Power Module (HF) PC6. John Deere System Advisory.

BCU 523691.05 (BCU )

Code: 523691.05



Error code BCU 523691.05 is triggered when the Power Module (High Frequency) PC6 in a John Deere vehicle measures a current of less than 500 mA at lead 1034 for the lower worklights on the cab frame (E20 or E36), while these lights are switched on. This diagnostic trouble code indicates an open circuit, which could be due to disconnected wires, a broken circuit, or faulty light fixtures, preventing the worklights from receiving sufficient power for operation.


Due to this open circuit condition, the lower worklights on the cab frame may fail to illuminate when activated, which could reduce visibility and affect safe operation, especially in low light conditions.


  • Inspect Worklight Fixtures and Wiring: Check the worklight fixtures and associated wiring for any signs of damage, disconnection, or wear that could be causing the open circuit.
  • Test Electrical Connections: Use a multimeter to test the continuity and voltage output at lead 1034 to determine the exact location and nature of the open circuit.
  • Repair or Replace Faulty Components: Repair any breaks or replace damaged wires or components that are contributing to the open circuit. Ensure all connections are secure and properly insulated.
  • Reset the Power Module PC6: After repairs are completed, reset the power module to clear the error code and to ensure that the module recognizes the restored circuit integrity.
  • Test System Functionality: Turn on the lower worklights to verify that they are receiving adequate current and are functioning correctly. Monitor the system to ensure there are no further issues with current delivery.
  • Regular Maintenance and Checks: Incorporate regular checks of the electrical system into the vehicle’s maintenance routine to prevent similar issues in the future. This includes inspecting wiring and connections for signs of damage or wear regularly.


Maintaining the electrical integrity of key operational features such as worklights is critical for the safe operation of heavy machinery. Regularly ensuring that all electrical systems are functioning properly is a vital part of preventive maintenance, which helps avoid operational downtime and enhances the safety and effectiveness of the machinery in various operating conditions.