Fendt 5.1.32 – A004 Control Console: A004 - 4WD automatic key — Key/A004 signal fault

This fault code indicates a signal error originating from the 4-Wheel Drive (4WD) automatic engagement button/key. The system is receiving an invalid, missing, or out-of-range signal from this specific switch. The tractor's '4WD automatic mode' is disabled, but other functions remain active and the operator can still manually engage '100% 4-WD'.

• 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 300 Vario (COM III)
• Fendt 400 Vario (COM III) / Farmer 400
• Fendt 700 Vario (COM III) / Favorit 700
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III) / Favorit 900

1. 1

   Physical Inspection: Inspect the 4WD automatic key on the A004 control console. Check for physical damage, sticking, or debris lodged around the button that might cause a continuous or blocked signal.

2. 2

   CAN Bus & Power Supply Check: Verify the voltage supply to the CAN bus. Check the fuse board A013, specifically fuses F040 and F041, which supply power to the A004 control console and A002 module.

3. 3

   Wiring & Connector Inspection: Inspect the wiring harness and connectors between the A004 console and the A002 ECU. Look for loose pins, corrosion, or chafed wires that could interrupt the signal.

4. 4

   Live Data Monitoring: Connect the FENDIAS diagnostic tool to monitor the live state of the 4WD automatic switch. Press the button to see if the state changes in the software; if it does not, the internal switch contact is likely failed.

1. 1

   Disconnect Power

   Turn off the tractor ignition and disconnect the battery to prevent electrical shorts during the repair.

2. 2

   Clean the Switch

   If the 4WD automatic button feels sticky, use a plastic-safe electrical contact cleaner around the edges of the key. Work the button gently to free any internal debris.

3. 3

   Check Connections

   Remove the trim around the A004 control console to access the wiring harness underneath. Disconnect the main harness, inspect the pins for oxidation, clean with contact cleaner, and securely reconnect.

4. 4

   Test Operation

   Reconnect the battery, turn on the ignition, and attempt to clear the stored 5.1.32 fault code using the tractor's terminal or FENDIAS software. Test the 4WD automatic button.

5. 5

   Replace or Repair Console

   If the fault immediately returns and the wiring to the A002 ECU tests good, the internal circuit board or membrane of the A004 control console has failed. Because individual buttons are generally not serviceable, the A004 console must be removed and either replaced with a new unit or sent to an agricultural electronics specialist for board-level repair.