Fendt 0B.1.21 – A050 - ECU, basic control unit: A050 - ECU, basic control unit TEACH-IN: Internal communication error.

This code indicates an internal communication failure within the tractor's main control unit, specifically affecting the "TEACH-IN" system (also known as the Headland Management System or Variotronic TI). When this fault is active, the automated sequence functions for headland turns will be restricted or completely non-operational.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• 300 Vario Series (COM III)
• 400 Vario Series (COM III)
• 411
• 412
• 415
• 700 Vario Series (COM III, SCR)
• 711
• 712
• 714
• 716
• 800 Vario Series (COM III, SCR)
• 815
• 817
• 818
• 820
• 900 Vario Series (COM III, SCR, Gen6)
• 916
• 922
• 924
• 927
• 930
• 933
• 936
• 939

1. 1

   Check for accompanying CAN bus faults (e.g., 0B.1.22 or 0B.1.23). If multiple modules are failing to communicate, the issue may be a damaged CAN bus harness (G-Bus) rather than the ECU itself.

2. 2

   Verify power supply (KL30 battery voltage, KL15 switched ignition) and earth/ground (KL31) at the A050 ECU connectors to rule out voltage drops causing internal processing errors.

3. 3

   Attempt to clear the fault using the FENDIAS diagnostic tool by deleting the Teach-In sequence data and re-initializing to rule out a software glitch or corrupted memory.

1. 1

   Connect diagnostic interface

   Connect the AGCO CANUSB interface and launch the FENDIAS diagnostic software.

2. 2

   Save configuration data

   Save the tractor's current configuration data if the ECU is still partially readable.

3. 3

   Perform EOL programming

   Perform an EOL (End of Line) programming on the A050 ECU. This reflashes the operating software and re-initializes the Teach-In sequence data storage.

4. 4

   Test system

   Cycle the ignition and test the Headland Management System.

5. 5

   Evaluate ECU hardware

   If fault 0B.1.21 returns immediately, the A050 ECU has suffered a permanent internal hardware failure (such as a failed EEPROM or internal bus transceiver) and must be replaced or sent to a specialist for board-level repair.

6. 6

   Replace A050 ECU

   Disconnect the tractor's battery. Locate the A050 Basic Control Unit (typically located in the right-hand console/cab electronics area). Carefully disconnect the multi-pin wiring harness connectors (e.g., X1402, X1404, etc.). Unbolt the module from its mounting bracket and install the replacement unit.

7. 7

   Perform post-installation programming

   A new A050 ECU is blank. You must use FENDIAS to perform EOL programming to write the tractor's specific chassis number and configuration to the module. You will also need to pair the new A050 with the A077 Immobilizer ECU and A051 Engine Control Unit, followed by a full transmission and steering calibration.