ATC 524219.04 – B143 Defog Sensor, Voltage Too Low. John Deere System Advisory.

ATC 524219.04 (ATC )

Code: 524219.04



The error code, ATC 524219.04, is triggered when the control unit detects that the voltage at the signal input for the defog sensor (B143, lead 2003) is too low, suggesting that the circuit is shorted to ground. This low voltage can impair the sensor’s functionality, affecting its ability to accurately detect window fogging conditions.


The low voltage condition may cause the defogging system to malfunction, potentially leading to inadequate defogging of the vehicle’s windows. This can impair visibility and affect the safety of vehicle operations, especially under adverse weather conditions.


  • Inspect Sensor Wiring and Connections: Examine the wiring and connections for the defog sensor at lead 2003 to identify any signs of damage or grounding issues.
  • Measure Voltage Levels: Use a multimeter to check the voltage at the sensor’s signal input to confirm if it falls below the normal range, indicating a short to ground.
  • Locate and Repair Short Circuits: Identify the source of the short to ground and repair or replace any damaged wiring or components that are contributing to the issue.
  • Test Sensor Functionality: After addressing the electrical faults, test the defog sensor to ensure it operates correctly and can accurately detect conditions.
  • Reset System and Perform Functional Testing: Clear any fault codes from the system and conduct a comprehensive system check to verify that the defog sensor and the defogging system function properly under normal operating conditions.


Regular maintenance of the HVAC system’s sensors, such as the defog sensor, is vital for ensuring they provide reliable and accurate data for effective climate control within the vehicle. Promptly correcting issues like voltage irregularities is crucial to maintaining the system’s performance and ensuring the safety and comfort of the vehicle’s occupants.