Fendt 6.1.B6 – A004 - ECU, Control Panel: Communication fault or signal fault with the 540 rpm speed selector key/button

The system detects an electrical or mechanical fault with the 540 rpm speed selector button (e.g., the button signal is missing, or the button has been stuck/pressed for more than 30 seconds). Because of this communication failure, the rear PTO speed cannot be modified or selected, and FENDIAS diagnosis may not be possible for that specific circuit.

• 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 series (409, 410, 411, 412)
• Fendt Favorit 700 series (711, 712, 714, 716)
• Fendt Favorit 900 series (916, 920, 924, 926, 930)
• 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

   Mechanical Button Check: Inspect the 540 rpm speed selector button on the A004 control panel. Ensure it springs back freely (fault triggers if stuck/pressed > 30s).

2. 2

   Voltage & Fuse Check: Verify the 12V power supply to the A004 control panel. Check the fuses on the A013 printed circuit board (specifically check fuses F040, F041, and fuses 32/33 depending on your exact model year).

3. 3

   Wiring & Harness Inspection: Consult wiring diagram Sheet 32 (Rear PTO). Check the wiring harness between the 540 rpm selector switch and the A004 ECU for continuity, shorts to ground, or corroded pins.

4. 4

   CAN Bus Communication: Verify that the A004 control panel is communicating properly with the A002 (Enhanced Control ECU) on the CAN bus.

1. 1

   Disconnect Power

   Turn off the tractor ignition and disconnect the battery to prevent electrical spikes.

2. 2

   Access the Control Panel

   Carefully remove the trim surrounding the A004 Operating Console/Control Panel in the cab to access the rear wiring connectors.

3. 3

   Test the Switch

   Using a multimeter, test the 540 rpm PTO speed selector switch for proper open/closed continuity when pressed.

4. 4

   Clean Contacts

   If the switch is sticking or shows high resistance, try cleaning the switch contacts with electronic contact cleaner.

5. 5

   Replace Component

   If the switch itself has failed electrically or mechanically, replace the switch. If the switch tests fine but the wiring harness has a break, repair the damaged wire. If the wiring and switch are intact but the fault persists, the internal communication board of the A004 ECU Control Panel has failed and the panel will require replacement or professional remanufacturing.

6. 6

   Clear Codes

   Reconnect the battery, turn on the ignition, and use the tractor's terminal or FENDIAS diagnostic tool to clear the stored 6.1.B6 fault code. Test the PTO engagement to ensure the 540 rpm speed can now be selected.