BCU 523758.11 – Unrealistic Value Detected from S121 Remote Control Switch for Rear PTO (Right). John Deere System Advisory.

BCU 523758.11 (BCU )

Code: 523758.11



The diagnostic trouble code BCU 523758.11 is generated when the Body Control Unit (BCU) detects an unrealistic value from the S121 remote control switch for the rear Power Take-Off (PTO) on the right side. This error typically indicates a fault in the switch itself or in its connection to the BCU, which could be due to wiring issues, a malfunctioning switch, or interference affecting the switch’s signal.


The system may temporarily disable the function of the rear PTO to prevent incorrect operation based on the faulty signal received. An error message or alert may also be displayed to inform the operator of the issue and prevent potential equipment damage or safety risks.


  • Inspect the S121 Switch and Wiring: Thoroughly check the S121 remote control switch and associated wiring for signs of damage, corrosion, or loose connections that could affect signal integrity.
  • Test the Switch Operation: Use diagnostic tools to test the functionality of the switch. Measure the signal output to ensure it aligns with expected values for given switch positions.
  • Replace or Repair Faulty Components: If the switch or wiring is found to be defective, replace or repair these components to restore proper function.
  • Verify Signal Integrity: After repairs, check that the signal from the switch to the BCU is clear and within the expected parameters to ensure reliable operation.
  • Reset the System and Re-test: Clear any fault codes from the BCU and test the system to ensure that the rear PTO operates correctly with the remote control switch.


Regular maintenance and proactive checks of control switches and their wiring are essential for ensuring the reliability and safety of PTO operations on agricultural machinery. Timely identification and resolution of issues like unrealistic signal values can prevent operational disruptions and maintain the effectiveness and safety of machinery use.