Fendt 9.1.C1 – A004 - ECU, control panel: Key fault or Faulty button (Automatic system)

The system detects an electrical or mechanical failure with the automatic mode button, meaning the button signal is either missing, implausible, or stuck. As a result, the automatic mode will not function, and the front power lift cannot be raised or lowered properly using the automatic controls.

• 409 Vario
• 410 Vario
• 411 Vario
• 412 Vario
• 711 Vario
• 712 Vario
• 714 Vario
• 715 Vario
• 716 Vario
• 717 Vario
• 718 Vario
• 916 Vario
• 920 Vario
• 924 Vario
• 926 Vario
• 930 Vario
• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• Fendt Farmer 400 series
• Fendt Favorit 700 series
• Fendt Favorit 900 series (e.g., 916, 920, 924, 926, 930 Vario)
• Fendt 300, 400, 700, 800, and 900 Vario (COM III) series

1. 1

   Inspect the automatic mode button on the joystick/control console for physical damage, sticking, or accumulated dirt that might hold the button down.

2. 2

   Inspect the wiring harness and CAN bus connections between the A004 control panel and the joystick (A034) for continuity, corrosion, or loose pins.

3. 3

   Connect the FENDIAS diagnostic tool to monitor the live state of the button. Press the button to see if the A004 ECU registers the state change. If the state does not change, the fault is isolated to the button or its immediate wiring.

1. 1

   Disconnect Power

   Always disconnect the tractor's battery before performing electrical repairs to prevent short circuits.

2. 2

   Access the Joystick/Button

   If diagnostics point to a failed button, you will need to access the joystick assembly.

3. 3

   Remove the Old Button

   According to repair documentation, the factory buttons are often melted or plastic-welded into the lower part of the joystick housing. To remove a faulty button without replacing the entire joystick, carefully dismantle the old button (repairers often use a small chisel or rotary tool to break the factory melt/weld).

4. 4

   Install the Replacement Button

   Fit the new replacement button (often a 12mm diameter switch) into the housing. Splice or solder the wiring connections securely.

5. 5

   ECU/Console Repair (If Applicable)

   If the button and wiring are intact but the A004 ECU is internally faulty, the A004 control console must be removed. These units can often be sent to specialized agricultural electronics repair centers (such as Micro Network) for circuit board repair, or replaced entirely.

6. 6

   Reassembly and Testing

   Reconnect the battery, clear the 9.1.C1 fault code using FENDIAS, and test the automatic switching function to ensure the front power lift operates correctly.