BCU 000168.03 – Control Unit Supply Voltage Too High. John Deere System Advisory.

BCU 000168.03 (BCU 168.03)

Code: 000168.03

Shortcode: 168.03


Error code BCU 000168.03 is set off when the Basic Control Unit (BCU) of a John Deere vehicle detects a supply voltage that exceeds 16 volts. This unusually high voltage can be hazardous as it may lead to overcharging, potentially damaging electronic components, affecting system performance, and reducing the lifespan of the battery and other electrical parts.


To prevent damage from the high voltage, the BCU may initiate protective measures such as disabling certain electrical systems or triggering warning indicators to alert the operator of the overvoltage condition.


  • Inspect Alternator and Voltage Regulator: The most common cause of high voltage in vehicle electrical systems is a malfunctioning alternator or voltage regulator. Check these components for faults and ensure they are functioning within specification.
  • Check Wiring and Electrical Connections: Inspect the wiring harness and connections for any signs of damage, wear, or poor connections that might affect voltage regulation.
  • Test Electrical System: Use a multimeter or a specialized diagnostic tool to measure the voltage levels throughout the electrical system, particularly at the BCU supply input, to confirm the overvoltage condition.
  • Replace Faulty Components: If the alternator, voltage regulator, or any related component is found to be faulty, replace it to correct the voltage irregularities.
  • Reset the BCU and Clear Fault Codes: After repairs, reset the BCU to clear any stored fault codes. This reset will also help verify that the issue is resolved by ensuring that the system does not immediately re-register the same fault.


Maintaining correct voltage levels is crucial for the safety and efficiency of the vehicle’s electrical systems. Regular monitoring of these systems and prompt attention to any voltage irregularities can prevent costly damage and ensure the reliable operation of your John Deere equipment.