Fendt 0B.1.23 – A050 - ECU, basic control unit: Communication error between MFA and TEACH-IN

The CAN bus data transfer between the multifunction armrest (A039 - MFA) and the headland management system program (TEACH-IN) has failed or been interrupted. As a direct consequence, the TEACH-IN function becomes 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
• Fendt 300 Vario (COM III)
• Fendt 400 Vario (COM III)
• Fendt 700 Vario (COM III / SCR)
• Fendt 800 Vario (COM III / SCR)
• Fendt 900 Vario (COM III / SCR)
• Fendt 919
• Fendt 922
• Fendt 924
• Fendt 927
• Fendt 930
• Fendt 933
• Fendt 936

1. 1

   Verify Symptoms: Confirm that the TEACH-IN (Headland Management) system is non-operational. Check if the tractor is logging related codes, such as 0B.1.25 (MFA does not report to bus) or 0B.1.41 (Internal communication saving or read-out error), which point to a broader bus failure.

2. 2

   CAN Bus Wiring Inspection: Inspect the CAN bus wiring harness connecting the A050 Basic Control Unit to the A039 Multifunction Armrest. Look for chafed wires, pinched cables, or rodent damage.

3. 3

   Connector Checks: Disconnect the harness at both the A050 ECU and the A039 MFA. Inspect the pins for corrosion, moisture ingress, or pushed-out pins.

4. 4

   Voltage/Resistance Testing: Measure the CAN bus voltage levels at the sockets to ensure the data lines are not shorted to ground, shorted to power, or open.

1. 1

   Wiring Repair

   If any breaks, shorts, or high-resistance areas are found in the CAN bus wiring between the A050 and A039, repair the harness or replace the affected pigtail/connector.

2. 2

   Software/Programming

   If the physical connections are sound, the issue may be a software corruption. Connect the FENDIAS diagnostic tool and perform an EOL (End of Line) programming sequence on the A050 Basic Control Unit to re-initialize the TEACH-IN sequence data.

3. 3

   Module Replacement/Repair

   If EOL programming fails or the module is unresponsive, the hardware inside the A050 ECU or the A039 MFA has likely failed. The defective unit must be removed and either sent to a specialized agricultural electronics repair facility (such as Ilgenfritz Mechatronics) or replaced with a new OEM unit.

4. 4

   Calibration

   If the A050 or A039 is replaced, you must use FENDIAS to program the new module to the tractor and calibrate the armrest controls (joystick, crossgate lever, etc.).