ACU 524020.31 – Transmission Engaged at Startup

ACU 524020.31 (ACU )

Code: 524020.31



This error code, ACU 524020.31, occurs when the Reversible Handle Reverser (RHR) is not set to PARK at the time of power-up, resulting in the transmission being inadvertently engaged. This condition poses a risk of unintended machinery movement upon startup.


To mitigate potential risks and ensure safety, the control unit automatically commands the transmission to shift to PARK as soon as the power-up condition is detected with the RHR not in the correct position.


  • Ensure that the RHR is always set to PARK before shutting down the equipment to prevent this issue upon the next startup.
  • Inspect the RHR mechanism and its linkage for any mechanical issues that might prevent it from properly locking into the PARK position.
  • Check the sensor or switch that detects the RHR position for faults or failures that could misreport the lever’s actual position.
  • Use diagnostic tools to verify the correct operation of the RHR and its alignment with the control unit’s safety protocols.
  • If inconsistencies are found during these checks, recalibrate or replace the necessary components to ensure reliable detection and response to the lever’s position.
  • Conduct regular training sessions for operators to reinforce the importance of setting the RHR to PARK before power down and checking it upon startup.


Adherence to proper shutdown and startup procedures is essential for operational safety. Regular maintenance and checks of the RHR and its associated sensors can help avoid issues related to improper lever positions at startup, thereby enhancing safety and preventing equipment damage.