John Deere 168.04 – CCU: Unswitched Supply Voltage Low

The control unit has detected that the unswitched battery power supply voltage has dropped below the normal operational threshold (typically less than 9.0 Volts). This low voltage condition can impair the functionality of electronic components, causing the module to disable functions or enter a safety mode to protect the system's integrity.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8245R through 8400R
• 9230
• 9330
• 9430
• 9530
• 9630
• 9470RT
• 9520RT
• 9570RT
• 4930
• R4038

1. 1

   Attempt vehicle recovery by reducing the electrical load (turn off non-essential cab accessories/lights) or increasing engine RPM to see if the alternator can catch up and clear the low-voltage state

2. 2

   Visually inspect the area around the batteries and alternator for obvious signs of damage, loose belts, or accumulated debris

3. 3

   Power down the machine and check the CCU unswitched power fuses (e.g., F28 in the cab load center or the 70-amp CCU fuse in the rear cab fuse block)

4. 4

   Test the battery's health and state of charge, and check the alternator and voltage regulator to ensure they are outputting proper voltage (typically 13.5V - 14.2V while running)

5. 5

   Inspect the wiring harness and connectors supplying unswitched power to the CCU for chafed wires, corrosion, or loose ground connections

6. 6

   Measure the voltage directly at the CCU input pins. If the voltage is below 9.0V but the battery tests at 12V+, the issue is isolated to the wiring harness or a bad ground

1. 1

   Cycle Power

   Turn off the tractor, wait a few moments, and cycle the key switch. Sometimes a temporary voltage dip during a heavy load will trigger the code, and a restart will clear it.

2. 2

   Clean Connections

   Disconnect the negative and positive battery cables. Clean the battery terminals, cable ends, and chassis ground points with a wire brush to ensure solid electrical contact. Reconnect and tighten.

3. 3

   Replace Blown Fuses

   If the CCU fuse is blown, inspect the harness for a short to ground before replacing the fuse. Replace with the exact OEM amperage rating.

4. 4

   Repair Wiring

   If a voltage drop is found between the battery and the CCU, repair or replace the damaged section of the wiring harness or the corroded connector.

5. 5

   Replace Charging Components

   If the battery fails a load test, replace it. If the alternator fails to maintain voltage under load, replace the alternator.

6. 6

   Clear Codes

   After repairs, turn the key on, clear the fault codes via the CommandCenter display, and start the engine to verify the code does not return.