BCU 523704.02 – B20 Left Draft Sensor, Distorted Signal During Calibration. John Deere System Advisory.

BCU 523704.02 (BCU )

Code: 523704.02



Error code BCU 523704.02 is activated when the Basic Control Unit (BCU) of a John Deere vehicle detects a voltage fluctuation exceeding 0.5 volts at the signal input of the left draft sensor during calibration. This diagnostic trouble code points to a malfunction within the draft sensor circuit, potentially caused by issues such as electrical interference, a faulty sensor, or compromised wiring.


The distorted signal can lead to inaccurate readings from the left draft sensor, potentially affecting the tractor’s hitch control system. This may compromise the tractor’s ability to precisely control and adjust the hitch, impacting performance and operational effectiveness.


  • Inspect the Left Draft Sensor and Wiring: Examine the left draft sensor and its associated wiring for any signs of damage, corrosion, or loose connections that could contribute to signal distortion.
  • Test Sensor Voltage: Use a multimeter to measure the voltage at the draft sensor’s input during calibration to verify the fluctuation and identify the source of the problem.
  • Replace or Repair Faulty Components: If the sensor or any part of its wiring is found to be faulty, undertake repairs or replace the damaged parts to ensure the integrity of the draft sensor circuit.
  • Re-calibrate the Draft Sensor: After repairing or replacing the necessary components, recalibrate the left draft sensor to ensure it provides accurate data to the BCU.
  • Reset the BCU: Clear any stored diagnostic trouble codes and reset the BCU to ensure it recognizes the repaired system and to reinitialize its settings.
  • Test System Functionality: Conduct functional tests to confirm that the draft sensor now operates correctly and provides stable and accurate readings during calibration.
  • Regular System Checks and Maintenance: Schedule routine inspections and preventive maintenance for the draft sensor and its circuitry to prevent future issues. Regular monitoring can help detect potential problems early, reducing downtime and maintenance costs.


Maintaining the accuracy and reliability of sensors in agricultural equipment is crucial for precision farming operations. Sensors like the draft sensor play a key role in automating and optimizing the performance of machinery. Ensuring that these sensors are functioning correctly through regular maintenance and timely repairs is essential for maximizing the efficiency and reliability of the equipment.