Fendt 4.1.A5 – Transmission Control Unit (TCU): Initial Reference (Zero Position) could not be reached or found during ignition "ON"

When the tractor's ignition is turned on, the A009 actuator unit attempts to locate its reference point (the approximate neutral point between forward and reverse travel). If the actuator fails to reach this position within the expected parameters, the system logs this code and restricts the tractor to emergency mode (auxiliary operation).

• 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 300 Vario series (COM III)
• Fendt 400 Vario series (Farmer 400)
• Fendt 700 Vario series (Favorit 700)
• Fendt 800 Vario series
• Fendt 900 Vario series (Favorit 900, 900 Vario COM III)

1. 1

   Check the ease of movement of the adjustment device using the emergency control system.

2. 2

   Verify that the CAN-bus data communication to the transmission control unit is intact, as wiring issues can prevent the actuator from reporting its position.

3. 3

   Check for logical errors or signal faults from the incremental encoder, which would prevent the zero position from being registered.

4. 4

   Inspect the actuator shaft and the transmission adjustment linkage for physical obstructions, binding, or heavy dirt accumulation that could physically prevent the motor from reaching the zero position.

1. 1

   Engage Emergency Mode

   Turn off the tractor, then use the mechanical emergency control system to manually actuate the transmission adjustment device.

2. 2

   Test Mechanical Linkage

   Move the mechanism by hand to ensure it operates smoothly. If it is jammed or stiff, clean, lubricate, or repair the mechanical linkage and actuator shaft.

3. 3

   Inspect the Actuator Unit (A009)

   If the mechanical linkage moves freely, the fault lies within the A009 actuator unit itself (which comprises a 12V DC electric motor, planetary gear, clutch, and the incremental encoder).

4. 4

   Replace the Actuator Unit

   If the internal encoder or motor has failed, remove the old A009 actuator unit and install the replacement unit.

5. 5

   Re-calibration / EOL Programming

   After installing a new actuator unit, perform an End-Of-Line (EOL) programming or Teach-In procedure using the FENDIAS diagnostic tool so the new unit can learn the transmission's zero reference point.