CAB 523841.04 – Secondary Brake Sensor Voltage Low

CAB 523841.04 (CAB )

Code: 523841.04



The fault code CAB 523841.04 occurs when the CAB control unit identifies that the voltage at the secondary hand brake lever position sensor is lower than normal. Low sensor voltage can result from issues such as poor electrical connections, degraded wiring, or a failing sensor. This specific code applies to the secondary brake system, which acts as an auxiliary braking system in European versions of the equipment, distinct from the parking brake.


No immediate action is taken by the control unit in response to this low voltage condition, relying instead on manual diagnostics and intervention to correct the issue.


  • Inspect Sensor and Wiring: Carefully examine the sensor and its wiring for any signs of wear, damage, or corrosion that could cause a reduction in voltage. Check for loose or disconnected wires that might be affecting the sensor’s performance.
  • Test Electrical Connections: Use a multimeter to check the voltage levels at the sensor connections. This can help confirm whether the issue is localized at the sensor or if it might be a broader electrical system problem.
  • Evaluate Power Supply and Ground Connections: Ensure that the sensor’s power supply and ground connections are secure and functioning correctly. Faulty power supply or ground connections can often lead to low voltage readings.
  • Replace Sensor if Necessary: If the sensor continues to show low voltage readings despite all connections being intact and correct, consider replacing the sensor to rectify the fault.
  • Monitor System Post-Repair: After any necessary repairs or replacements, monitor the system to ensure that the voltage has returned to normal operational levels and that the issue has been fully resolved.


Maintaining accurate voltage levels at all sensors is crucial for the proper functioning of vehicle safety systems like the secondary brake. Routine maintenance and timely repair of electrical components are essential to avoid disruptions in sensor operation and ensure the reliability and safety of the braking system.

Control Units: John Deere

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