ACU 523961.02 – Improper Park Engagement

ACU 523961.02 (ACU )

Code: 523961.02



This error code, ACU 523961.02, is triggered when the park mechanism is engaged while the vehicle remains in gear. This issue generally indicates a failure in the Power Take-off Interface (PTI) system, which should prevent such a condition.


To safeguard against potential damage or unsafe conditions due to conflicting transmission settings, the control unit automatically defaults the system to neutral.


  • Verify the functionality of the PTI system to ensure it is correctly preventing the engagement of park while the vehicle is in gear. Check for any fault codes specific to the PTI system.
  • Inspect the transmission controls and park engagement mechanisms for any mechanical faults or improper configurations that might allow park to be engaged while in gear.
  • Conduct a comprehensive diagnostic to assess the interaction between the gear selection and park engagement systems. This may involve using specialized diagnostic tools to monitor and test the control signals.
  • Reset or recalibrate the transmission and parking systems according to the manufacturer’s guidelines to ensure proper synchronization and operation.
  • If resetting and recalibration do not resolve the issue, consult with a John Deere technician for further in-depth analysis and possible repairs or replacement of faulty components.


This condition should not normally occur if all systems are functioning correctly. Regular maintenance and prompt attention to any PTI or transmission anomalies are crucial to prevent this and similar issues.