Fendt 6.1.01 – Enhanced Control System (A002 ECU): A004 - Rear PTO ON / OFF key in cab — Key / A004 signal fault.

This indicates a signal fault originating from the Rear PTO ON/OFF button located on the control console, or a CAN-bus communication failure between the control console and the enhanced control unit. When this fault is triggered, the tractor's safety protocol automatically disengages the rear PTO.

• 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 series
• Fendt Favorit 700 Vario series
• Fendt Favorit 900 Vario series
• Fendt 300, 700, 800, and 900 Vario COM III series

1. 1

   Check CAN-Bus Voltage: Verify the voltage supply for the CAN-Bus on the A013 fuse board. Specifically, check fuses F040 and F041.

2. 2

   Inspect the Switch: Physically inspect the yellow Rear PTO ON/OFF button on the A004 control console. Check for sticking, physical damage, or debris preventing full travel (total button travel should be ~5 mm).

3. 3

   Wiring & Continuity: Refer to the "PTO's" circuit diagram (Sheet 32). Check the wiring harness and connectors between the A004 Control Console (in the cab on the right mudguard) and the A002 Enhanced Control ECU for continuity, chafing, or corrosion.

4. 4

   Emergency Override Test: Test if the PTO can be engaged by pressing and holding the emergency PTO key in the cab for 5 seconds. If it engages, the mechanical PTO components are functioning, isolating the issue to the A004 switch/signal circuit.

1. 1

   Power Down

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

2. 2

   Replace Fuses (If Applicable)

   If fuses F040 or F041 on the A013 board are blown, replace them and re-test the system.

3. 3

   Access the A004 Console

   Remove the right mudguard panel in the cab to access the A004 Control Console and its wiring separation points.

4. 4

   Repair Wiring

   If continuity tests failed during diagnostics, repair or replace the damaged sections of the CAN-bus wiring harness between A004 and A002.

5. 5

   Replace the Switch/Console

   If the yellow PTO push button is faulty, disconnect the AMP Superseal plug and pop the switch out of the console to replace it. Note: On some Vario configurations, if the internal ECU of the A004 control console has failed (internal RAM/EEPROM or bus controller failure), the entire A004 control console unit must be replaced.

6. 6

   Clear Codes

   Reconnect the battery, turn the ignition ON, and use the FENDIAS or SERDIA diagnostic tool to clear the fault code from the A002 Enhanced Control ECU. Test the PTO engagement.