BCU 000168.17 – Control Unit Supply Voltage Too Low at High Engine Speed. John Deere System Advisory.

BCU 000168.17 (BCU 168.17)

Code: 000168.17

Shortcode: 168.17


Error code BCU 000168.17 is triggered when the Basic Control Unit (BCU) of a John Deere vehicle detects that the supply voltage has dropped below 12.5 volts while the engine speed exceeds 1500 rpm. This scenario suggests a potential issue with the vehicle’s charging system, particularly at higher engine speeds, which could include problems with the alternator, voltage regulator, or associated wiring.


In response to this low voltage condition at high engine speeds, the BCU may limit the functionality of certain electrical components to conserve power and protect sensitive electronics, which could affect the vehicle’s operational efficiency and safety.


  • Inspect the Charging System: Check the alternator and voltage regulator for functionality. These components are crucial for maintaining adequate voltage, especially at higher engine speeds. Test the alternator output with a multimeter while the engine is running at various speeds to ensure it meets the specifications.
  • Examine Electrical Connections: Ensure that all connections in the charging system are secure and free from corrosion. Poor connections can lead to voltage drops, particularly under load.
  • Check Battery Condition: Verify that the battery is in good health and capable of holding a charge. A weak battery may not maintain voltage under higher engine loads.
  • Test and Replace Belts: Inspect the drive belts for wear and tension. A loose or worn belt can prevent the alternator from spinning fast enough to produce the required voltage at higher engine speeds.
  • Reset the BCU and Monitor: After making any necessary repairs or adjustments, reset the BCU to clear the fault code and monitor the voltage under normal operating conditions to ensure the issue is resolved.


Maintaining a stable supply voltage is essential for the proper functioning of all electrical components in your John Deere equipment. Regularly monitoring and maintaining the charging system, especially the alternator and voltage regulator, is critical to preventing voltage-related issues that can lead to operational inefficiencies and increased wear on electrical components.