AIC 521277.09 – LIN Bus 4 Fault. John Deere AIC System Alert.

AIC 521277.09 (AIC )

Code: 521277.09



This diagnostic code, AIC 521277.09, is reported when there is a communication failure within the LIN Bus 4 system, as indicated by incorrect or no data transmission from the LIN Bus Module located at Positions F or G. This issue points to potential problems in the LIN Bus itself or faults in the transmitting module, leading to disruptions in the flow of data necessary for the operation of various vehicle systems.


In response to this critical fault, the control unit has reduced certain functionalities linked to LIN Bus 4 to avoid incorrect or unsafe operations, maintaining system integrity.


  • Thoroughly inspect the LIN Bus 4 pathways, particularly at Positions F and G, for any signs of physical damage, disconnections, or deterioration that might affect communication.
  • Utilize specialized diagnostic equipment to assess the continuity and performance of the LIN Bus 4. Identify any disruptions or anomalies in signal transmission that could be responsible for the communication faults.
  • Examine the configurations and operational settings of the LIN Bus modules involved to ensure they are properly set up for accurate data exchange within the network.
  • If defects or malfunctions are identified in any modules or network components, undertake necessary repairs or replacements to restore full communication capabilities.
  • Once the necessary corrective actions are implemented, recalibrate any affected systems and perform rigorous testing to confirm that all functionalities reliant on LIN Bus 4 are fully operational and stable.


Effective management and maintenance of LIN Bus networks are essential for the seamless integration and functioning of the vehicle’s control systems. Regular monitoring and timely rectification of communication issues are crucial to maintaining the reliability and efficiency of these systems, thus preventing operational disruptions.