Fendt 8.3.23 – A004 - ECU, control panel: Signal line fault for the Rear EPC 'Depth control' setpoint setting

The system has detected an invalid signal, missing signal, or electrical fault coming from the depth control rotary knob/potentiometer. This triggers a 'Control locked' state, meaning the rear Electronic Power Control (EPC) / rear power lift is terminated and locked out from operating.

• 409 Vario
• 410 Vario
• 411 Vario
• 412 Vario
• 711 Vario
• 712 Vario
• 714 Vario
• 715 Vario
• 716 Vario
• 717 Vario
• 718 Vario
• 916 Vario
• 920 Vario
• 924 Vario
• 926 Vario
• 930 Vario
• 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
• Farmer 400
• Favorit 700
• Favorit 900
• FENDT 700 Vario
• FENDT 800 Vario
• FENDT 900 Vario
• FENDT 300 Vario (COM III)
• FENDT 400 Vario (COM III)
• FENDT 700 Vario (COM III)
• FENDT 800 Vario (COM III)
• FENDT 900 Vario (COM III)

1. 1

   Connect the FENDIAS diagnostic tool and check the 'REAR EPC SETPOINT / POSITION SENSOR' data block to see if the signal from the depth control potentiometer is missing, erratic, or out of range.

2. 2

   Inspect the physical condition of the depth control rotary knob on the A004 control console for mechanical damage or liquid intrusion.

3. 3

   Consult the 'Electrohydraulic power lift control' circuit diagram for your chassis number and test the wiring harness and connectors between the depth control potentiometer and the A004 control console for continuity, open circuits, or shorts to ground.

4. 4

   Test the potentiometer's resistance/voltage sweep with a multimeter to determine if it has a dead spot or has failed internally.

1. 1

   Disconnect the tractor's battery

   Ensure safety while working on the electrical system.

2. 2

   Access the A004 control console

   Typically located on the right-hand mudguard or multifunction armrest, depending on the exact model.

3. 3

   Repair or replace the damaged section of the wiring harness

   Perform this if diagnostic tests proved the wiring is faulty.

4. 4

   Remove the faulty depth control setpoint potentiometer from the console

   Perform this if the potentiometer failed the multimeter test.

5. 5

   Install the new depth control potentiometer

   Securely reconnect the wiring harness.

6. 6

   Reassemble the A004 control console panels

   Reconnect the battery.

7. 7

   Clear the fault codes

   Use the FENDIAS diagnostic tool.

8. 8

   Perform the rear EPC calibration procedure

   Specifically Calibration 8001: rear EPC - depth control as specified in the Fendt workshop manual to teach the ECU the new potentiometer's minimum and maximum values.

9. 9

   Test the rear power lift operation

   Confirm the 'Control locked' status has cleared and full functionality is restored.