BCU 523691.09 – Lower Worklights on Cab Frame, Incorrect CAN Bus Message from BCU (Power Module HF PC6). John Deere System Advisory.

BCU 523691.09 (BCU )

Code: 523691.09



Error code BCU 523691.09 is triggered when there is a communication problem between the Power Module (High Frequency) PC6 and the Basic Control Unit (BCU) in a John Deere vehicle, specifically concerning the lower worklights on the cab frame. This diagnostic trouble code indicates that the CAN bus messages from the BCU to the power module PC6 are either intermittent or completely absent, which could be due to issues like loose wiring, connection failures, or other disruptions in the CAN bus network.


The system may exhibit inconsistent or faulty behavior of the lower worklights due to the unreliable data communication, potentially leading to operational inefficiencies or safety risks if the lighting does not function as expected during critical operations.


  • Inspect CAN Bus Connections: Check all CAN bus connections between the BCU and the power module PC6, particularly focusing on the connectors and wiring associated with the lower worklights. Ensure all connections are secure and free from corrosion or damage.
  • Test CAN Bus Communication: Utilize diagnostic tools to monitor and test the CAN bus communication between the BCU and PC6. Look for any errors or intermittent connections that could be causing the communication issues.
  • Resolve Wiring Issues: Repair or replace any faulty wiring or connectors identified during the inspection and testing phases. Ensure that the entire route of the CAN bus from the BCU to PC6 is intact and securely connected.
  • Reset the Power Module and BCU: After addressing any physical connection issues, reset both the power module and the BCU to clear any stored errors and to reinitialize the communication protocols.
  • Verify Correct Operation: Test the lower worklights to ensure they respond correctly to commands from the control unit. Monitor the CAN bus to confirm that messages are being transmitted and received without interruption.
  • Continuous System Monitoring: Implement regular checks of the CAN bus system to ensure ongoing reliability of communication, especially for systems critical to safety and operation such as lighting.


Effective communication across vehicle systems via the CAN bus is crucial for the integrated operation of modern agricultural machinery. Regular maintenance of these systems, including proactive checks and timely repairs of the communication networks, is essential to prevent operational disruptions and ensure the machinery operates safely and effectively in all conditions.