BCU 523919.09 – Inner Worklights on Front of Roof, Incorrect CAN BUS Message. John Deere System Advisory.

BCU 523919.09 (BCU )

Code: 523919.09



Diagnostic trouble code BCU 523919.09 is triggered when there is a communication issue between the power module PC0 and the Basic Control Unit (BCU) concerning the inner worklights on the front of the roof (E18/1). The problem involves intermittent or nonexistent reception of CAN (Controller Area Network) messages from the BCU to power module PC0, which may be caused by loose wiring, connectivity issues, or faults within the CAN BUS system itself.


This communication error may lead to improper functioning of the inner worklights, such as failing to turn on or off according to the operator’s commands. The system may alert the operator to this issue through diagnostic displays or warning lights.


  • Inspect CAN Bus Connections: Thoroughly check all CAN bus connections between the BCU and power module PC0. Ensure that they are secure and free from corrosion or damage.
  • Test Wire Continuity and Security: Use diagnostic tools to test the continuity of the wires involved in the CAN bus system. Focus on identifying any loose or intermittent connections that could be disrupting communication.
  • Resolve Connectivity Issues: Tighten or replace any loose or damaged connectors or wiring found during the inspection.
  • Check for CAN Bus Interference: Ensure that there is no electromagnetic interference affecting CAN bus communication. Keep wiring away from high voltage lines or equipment that may emit strong electromagnetic fields.
  • Reset and Reconfigure Systems: After ensuring all physical connections are intact and secure, reset the CAN bus system and reconfigure settings if necessary to ensure proper communication protocols are followed.
  • Monitor System Performance: Continuously monitor the system to ensure that communication has been fully restored and that no further message errors are occurring.


Maintaining clear and correct communication across the CAN bus is crucial for the efficient operation of all interconnected vehicle systems. Regular diagnostics and proactive maintenance can help avoid communication failures and ensure that the equipment operates smoothly and effectively. Ensuring clear and correct communication pathways within vehicle control systems is essential for operational reliability and accuracy.

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