Fendt 4.1.2E – Transmission Control Unit / Enhanced Control ECU (A002): Signal fault with the "v+ transmission control" (joystick forwards) on the A034 - Driving switch, CAN bus

The system detects a signal failure or electrical fault when the joystick is pushed forward to accelerate or command forward travel. The tractor will typically restrict normal driving functions and default to "Auxiliary Operation" (emergency mode).

• 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 (409, 410, 411, 412)
• Fendt 700 Vario (711, 712, 714, 716)
• Fendt 800 Vario (815, 817, 818)
• Fendt 900 Vario (916, 920, 924, 926, 930)

1. 1

   Inspect the A034 joystick for physical damage, sticking buttons, or debris that might prevent the 'v+' (forward) switch from operating smoothly

2. 2

   Use the Variotronic Ti terminal (Diagnostics Menu 1) or the FENDIAS service tool to monitor the 'IDEAL' target value for the transmission ratio, verifying if the value changes when the joystick is pushed forward

3. 3

   Check the CAN bus wiring harness between the A034 Driving switch and the A002 Enhanced Control ECU for chafing, pinched wires, or loose connector pins

4. 4

   Verify the power supply for the CAN bus by checking the fuses on the A013 printed circuit board (specifically F040, F041, or F047 depending on model year)

1. 1

   Resolve Wiring Issues

   If the diagnostic checks reveal a break or short in the CAN bus communication lines between the A002 ECU and the A034 joystick, repair the wiring harness.

2. 2

   Replace Fuses

   If the CAN bus power supply is dead, replace the blown fuse on the A013 circuit board and re-test the joystick.

3. 3

   Replace the Joystick

   If the wiring and power supply are intact but the "v+" signal failure persists (internal electrical fault), the A034 Driving switch must be replaced.

4. 4

   EOL Programming

   After installing a new A034 joystick, you must perform EOL (End of Line) programming / teach-in calibration using the FENDIAS diagnostic program or the tractor's terminal to sync the new joystick with the A002 ECU.