Fendt 0F.1.25 – A050 - ECU, basic control unit: Communication problem: no information from MFA (Hydr3 button, Hydr4 button)

The basic control unit is not receiving the expected CAN bus signals from the 3rd and 4th hydraulic circuit buttons located on the multifunction joystick/armrest.

• 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 series
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series
• 922
• 924
• 927
• 930
• 933
• 936

1. 1

   Use the tractor's terminal or FENDIAS diagnostic software to determine if the fault is currently active or just stored in the history. Clear the code and cycle the key to see if it returns immediately.

2. 2

   Inspect the 3rd and 4th hydraulic buttons on the multifunction joystick for physical damage, sticking, or debris preventing them from actuating properly.

3. 3

   Check the CAN bus wiring harness (specifically the Comfort/Control bus) between the A039 MFA and the A050 ECU. Look for chafed wires, pinched harnesses, or loose connector pins.

4. 4

   Verify that the A039 MFA is receiving proper power and ground supply, as a voltage drop can cause localized communication dropouts.

5. 5

   Connect FENDIAS and monitor the live data for the MFA. Press the Hydr3 and Hydr4 buttons to see if the state changes in the software. If other buttons register but these do not, the fault is isolated to the joystick's internal circuit board.

1. 1

   Disconnect Power

   Always turn off the battery disconnect switch before servicing electrical components or unplugging ECUs.

2. 2

   Harness Repair

   If diagnostic checks reveal damaged wiring between the A039 and A050 modules, repair the broken wires or replace the damaged connector pins.

3. 3

   Component Replacement

   If the wiring is intact but the Hydr3/Hydr4 buttons are unresponsive in FENDIAS, the A039 Multifunction Armrest (or the joystick sub-component) has an internal hardware failure and must be repaired or replaced. If the MFA is verified to be sending the signal but the A050 ECU is not processing it (and the CAN bus resistance measures a healthy 60 ohms), the A050 Basic Control Unit may have an internal fault requiring repair or replacement.

4. 4

   Reassembly and EOL Programming

   Reconnect all modules and restore battery power. If the A050 ECU or A039 MFA was replaced, you must perform EOL (End of Line) programming and calibration using FENDIAS so the tractor recognizes the new modules.

5. 5

   Clear Codes

   Clear the 0F.1.25 fault code from the A050 memory and test the hydraulic buttons to ensure the repair was successful.