Fendt 4.1.2C – Transmission Control / A002 ECU (Enhanced Control): Signal fault within the A034 - Driving switch (CAN bus joystick)

Fault code 4.1.2C indicates a signal fault within the A034 - Driving switch (CAN bus joystick), specifically pointing to a failure of the A003 button (Neutral/Active stationary mode toggle). When active, the tractor will typically be restricted to an emergency or auxiliary operation mode.

• 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 Vario
• Fendt Favorit 700 Vario
• Fendt Favorit 900 Vario
• Fendt 300 Vario
• Fendt 400 Vario
• Fendt 700 Vario
• Fendt 800 Vario
• Fendt 900 Vario

1. 1

   Consult the 'Transmission control' wiring diagram (typically Sheet 29 or 22/23, depending on your specific model's manual). Inspect the CAN bus wiring harness and connectors between the A034 joystick and the A002 Enhanced Control ECU for continuity, corrosion, or shorts.

2. 2

   Inspect the Neutral/Active Standstill button on the joystick for physical damage, sticking, or lack of tactile feedback.

3. 3

   Connect the FENDIAS diagnostic program to check for CAN communication errors, EOL (End of Line) programming errors, or checksum errors related to the A034 joystick.

1. 1

   Resolve Wiring Issues

   If the diagnostic checks reveal a break or short in the CAN bus connection between the A002 ECU and the A034 joystick, repair the wiring harness or replace the damaged connector pins.

2. 2

   Repair or Replace the Joystick

   If the wiring is intact but the signal failure persists, the internal circuit board or the button itself inside the A034 joystick is defective. You must either replace the entire joystick assembly or send the joystick to a specialized agricultural electronics repair service (such as Ilgenfritz Mechatronics) to have the internal microswitches and circuit board repaired.

3. 3

   EOL Programming

   If the joystick is replaced, or if the system suffered a data initialization error, you must run a new EOL (End of Line) programming procedure for the A034 joystick using the FENDIAS dealer diagnostic software.

4. 4

   Clear and Test

   Clear the fault codes and test the tractor to ensure the Neutral/Active Standstill button functions correctly and the tractor successfully exits auxiliary/emergency mode.