Fendt 5.1.31 – A004 Control Console: A004 - 4WD 100% key — Key/A004 signal fault

Signal failure or implausible reading originating from the manual 4-Wheel Drive (100% engagement) button. The system detects that the signal from this specific key to the control console is faulty (e.g., the button is shorted, physically stuck, or has an internal circuit break).

• 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
• Fendt Farmer 400 Vario
• Fendt Favorit 700 Vario
• Fendt Favorit 900 Vario
• Fendt 300 Vario series
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series
• Fendt Vario COM III generation models

1. 1

   Physical Inspection: Inspect the 4WD 100% button on the A004 control console. Check if the button is physically stuck, collapsed, or contaminated with debris/spilled liquids.

2. 2

   Fuse Check: Check the voltage supply for the CAN bus on the A013 printed circuit board/fuse board. Specifically, inspect fuses F040 and F041.

3. 3

   Live Data Monitoring: Connect the FENDIAS diagnostic tool to monitor the live state of the 4WD 100% key to see if it reads as permanently pressed or fails to register.

4. 4

   Wiring & Bus Check: Inspect the CAN bus wiring harness and connectors between the A004 Control Console and the A002 Enhanced Control ECU for chafing, corrosion, or loose pins.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes during module handling.

2. 2

   Access the Console

   Remove the trim panels on the right-hand armrest/mudguard to expose the underside of the A004 Control Console.

3. 3

   Inspect Connectors

   Disconnect the main wiring harnesses from the A004 console. Inspect the pins for green corrosion or moisture. Clean with electrical contact cleaner and reseat the connectors.

4. 4

   Test / Replace

   Send the A004 Control Console to a specialized agricultural electronics repair facility, or replace the entire A004 Control Console assembly.

5. 5

   Reassembly & Clearing

   Reinstall the console, reconnect the battery, and turn the ignition on. Use the tractor's terminal or FENDIAS software to clear the stored 5.1.31 fault code.

6. 6

   Verification

   Press the 4WD 100% key to ensure the 4WD engages properly and the code does not return.