Fendt 4.1.2B – Transmission Control Unit: Signal fault from Button for driving mode selection

Fault code 4.1.2B indicates a signal fault or failure originating from component A003 / A034, the driving mode selection button on the joystick. The tractor's safety protocol dictates that the actual driving mode remains engaged, and no further switching between modes is possible until the ignition is turned OFF and back ON.

• 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
• Favorit 900 series
• Favorit 700 series
• Farmer 400 series
• 900 Vario COM III

1. 1

   Connect FENDIAS software and monitor live data for the drive switch (A034/A003) to verify if button presses are registering.

2. 2

   Inspect the driving mode selection button on the joystick for physical damage, sticking, or debris preventing contact.

3. 3

   Check the wiring harness and CAN bus connections between the joystick (A003) and the Transmission Control Unit for continuity, shorts to ground, or corrosion.

1. 1

   Turn off the tractor ignition and disconnect the battery.

   Ensure the tractor is powered down before beginning the repair.

2. 2

   Carefully remove the side panel/cover on the armrest console to access the joystick mounting hardware.

   This provides access to the joystick assembly.

3. 3

   Disconnect the electrical harness plugs connecting the joystick to the tractor's CAN bus system.

   Safely unplug the connections.

4. 4

   Unbolt and remove the joystick/drive lever (A003) from the armrest.

   Remove the physical assembly from the console.

5. 5

   Repair or replace the joystick assembly.

   Options include replacing the specific membrane keypad/button board via aftermarket suppliers, sending the joystick to a specialized agricultural electronics repair service, or replacing the entire joystick assembly with a new OEM unit.

6. 6

   Install the repaired or new joystick, reconnect the wiring harnesses, and reassemble the armrest console.

   Put the components back together in reverse order of removal.

7. 7

   Reconnect the battery, turn on the ignition, and use FENDIAS to clear the fault codes.

   Test the driving mode selection button to ensure the tractor successfully switches between Range I and Range II.