BCU 523691.09 – Incorrect CAN BUS Message Affecting Lower Worklights on Cab Frame. John Deere System Advisory.

BCU 523691.09 (BCU )

Code: 523691.09



The diagnostic trouble code BCU 523691.09 is activated when there is a disruption in the data transfer between the power module (HF) PC6 and the Body Control Unit (BCU). This error manifests as intermittent or nonexistent reception of one or several CAN bus messages from the BCU to the power module (HF) PC6, potentially due to issues such as a loose wire. This communication error can impact the operational control and monitoring of the lower worklights on the cab frame (E20 or E36).


The BCU may trigger a fault response, temporarily disabling control or feedback from the affected worklights to prevent unpredictable behavior caused by incorrect or missing data messages.


  • Inspect CAN Bus Connections: Start with a thorough check of the CAN bus connections between the BCU and the power module. Ensure all connections are secure and free of corrosion.
  • Test Wire Continuity and Security: Use diagnostic tools to test the continuity of the wires involved in the CAN bus system. Pay special attention to any signs of loose wiring that could be causing intermittent connections.
  • Resolve Connectivity Issues: Tighten or replace any loose or damaged connectors or wiring found during the inspection.
  • Check for CAN Bus Interference: Ensure 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 reliable 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.