Fendt 4.1.A6 – Transmission Control Unit: Actuator Reference Point Signal Fault

The A009 actuator unit controls the actuator shaft to change the transmission ratio in the ML Vario transmission. The 4.1.A6 code indicates that the transmission control system lost the reference point signal from the actuator's incremental encoder during operation. When this occurs, the tractor enters emergency mode and the transmission is automatically locked to a maximum speed of approximately 30 km/h.

• 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
• 300 Vario COM III
• 400 Vario COM III
• 700 Vario COM III
• 800 Vario COM III
• 800 Vario S4
• 900 Vario Favorit 900
• 900 Vario COM III
• 900 Vario S4

1. 1

   Check fuse F3 in the X1440 fuse board

2. 2

   Inspect the physical mechanical linkage between the A009 actuator unit and the transmission actuator shaft for loose connections

3. 3

   Perform an emergency operation test by engaging emergency operation and checking for smooth adjustment action of the actuator

4. 4

   Test the electrical supply by connecting an adapter cable to the X037 separation point. Verify Pin 4 has 12 to 14 VDC and Pin 8 has a good Earth. Apply a load (e.g., 55W bulb) and verify voltage drop is max 1V

5. 5

   Verify the CAN bus wiring and check the transmission bus terminating resistors for communication drops

1. 1

   Access the component

   Locate the A009 actuator unit on the right side of the tractor, below the cab. On some models (like Favorit 900), unscrew and remove the right rear wheel and side panel for access.

2. 2

   Depressurize the system

   Operate the clutch pedal, handbrake, or neutral switch to depressurize the high-pressure circuit via the high-pressure-relief valves.

3. 3

   Disconnect wiring

   Disconnect the main electrical harness (X037 connector) from the A009 actuator unit.

4. 4

   Remove the actuator

   Unbolt the A009 actuator unit from the transmission control housing.

5. 5

   Install the new actuator

   Mount the replacement A009 actuator unit, ensuring the planetary gear and incremental encoder align properly with the transmission actuator shaft.

6. 6

   Reconnect and initialize

   Reconnect the electrical harness and turn the ignition ON so the new actuator unit can automatically search for the initial reference (zero position). Start the engine to allow the actuator to locate the precise neutral point.

7. 7

   Reassembly and testing

   Reinstall the side panel and the right rear wheel. Clear the fault codes using the tractor's diagnostic terminal and test drive to ensure smooth transmission ratio adjustments.