John Deere 158.01 – FCC: Switched Supply Voltage Low

Triggered when the control unit detects that the switched battery supply voltage (ELX) has fallen below 12.5 volts while the engine speed is above 1500 RPM for longer than 2 seconds.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 6110R-6215R
• 7210R-7310R
• 8235R-8360R
• 9370R-9620R
• 5090M
• 5100M
• 5115M
• 7830
• 326E
• 329E
• 4730

1. 1

   Inspect Battery Health: Check the battery voltage with a multimeter to ensure it is fully charged and capable of holding a charge. Perform a load test on the battery.

2. 2

   Examine the Alternator: Verify that the alternator is functioning correctly and providing adequate charging voltage (typically 13.5V - 14.5V) while the engine is running above 1500 RPM. Inspect the alternator belt for wear and proper tension.

3. 3

   Check Grounding Points: A common cause for this code is a poor ground. Check the main ground wire between the engine and the cab. Ensure the post where multiple grounds come together is secure and free of corrosion.

4. 4

   Examine Electrical Connections: Inspect all electrical connections related to the FCC, CLC, battery, and alternator. Look for loose, corroded, or damaged connections that could cause a voltage drop.

5. 5

   Monitor System Voltage: Use a multimeter or the tractor's CommandCenter display to monitor the system voltage during operation to see if it fluctuates or drops below 12.5V under load.

1. 1

   Clean and Tighten Connections

   Disconnect the battery. Clean the battery terminals, the alternator connections, and all major chassis/cab ground points with a wire brush. Reconnect and tighten them securely.

2. 2

   Replace Worn Charging Components

   If the alternator belt is loose or worn, replace or tension it. If the alternator fails a bench test or output test, replace the alternator.

3. 3

   Replace the Battery

   If the battery fails a load test or has a dead cell, replace it.

4. 4

   Inspect and Repair Wiring

   Trace the wiring harness supplying power to the Cab Load Center and the Front Console Control Unit. Repair any frayed, pinched, or damaged wires.

5. 5

   Clear Codes and Test

   Turn the key switch to cycle the tractor power. Start the engine, throttle up past 1500 RPM, and apply an electrical load (e.g., turn on flood lights and wipers). Verify that the voltage remains stable and the 158.01 code does not return.