Fendt 4.1.84 – JOYSTICK: A034 - Driving switch, CAN bus

A plausibility error where data transfer from the driving switch (main Vario joystick) is sending conflicting or illogical signals to the system. The default positions for Forward (F), Reverse (R), Forward/Reverse (FR), and the Tempomat (cruise control) do not match.

• 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
• 400 Vario series
• 700 Vario series
• 800 Vario series
• 900 Vario series

1. 1

   Visually inspect the wiring harness and connectors between the A034 joystick and the ECU for corrosion, moisture, or loose pins

2. 2

   Verify the power supply for the CAN bus circuit board by checking fuse F047 (and related fuses F040/F041)

3. 3

   Perform CAN bus multimeter checks: measure termination resistance (should be ~60Ω), check line voltages (CAN High 2.5–3.0 V, CAN Low 2.0–2.5 V), and test transceiver resistance to ground

4. 4

   Monitor live data from the A034 joystick using a diagnostic tool (like FENDIAS) to identify which specific button or axis is registering the implausible reading

1. 1

   Disconnect Power

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

2. 2

   Access the Joystick

   Remove the armrest/console covers to access the A034 driving switch assembly.

3. 3

   Inspect and Clean

   Disconnect the joystick's electrical connector. If corrosion is present, clean the contacts. If the wiring harness is damaged, repair the affected section.

4. 4

   Replace the Joystick

   If the wiring tests perfectly but the plausibility error remains, the internal microswitches or circuit board of the joystick have failed. Unbolt the defective A034 joystick and install the replacement unit.

5. 5

   Reassembly and Power Up

   Reconnect the electrical harness, reassemble the console, and reconnect the battery.

6. 6

   Calibration / Teach-in

   Access the tractor's diagnostic menu and perform the calibration procedure for the potentiometer/sliding switch on the A034 joystick (often referred to as code 4010).

7. 7

   Clear Codes

   Clear the 4.1.84 fault code using the diagnostic tool and test drive the tractor to ensure all directional and cruise control functions operate correctly.