Fendt 04.1.2D – Transmission Control System: Faulty forward travel signal

The system has detected a signal fault or plausibility error when the operator attempts to select forward travel using the steering column stalk (S079 switch). When this fault is active, the TMS (Tractor Management System) is automatically switched off.

• 309 Vario COM III
• 310 Vario COM III
• 311 Vario COM III
• 312 Vario COM III
• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• 309
• 310
• 311
• 312
• 409
• 410
• 411
• 412
• 711
• 712
• 714
• 715
• 716
• 717
• 815
• 817
• 818
• 820
• 916
• 919
• 920
• 922
• 924
• 925
• 926
• 927
• 930
• 933
• 936

1. 1

   Test Joystick Redundancy: Verify if the rapid reversing function still works via the multifunction joystick. If it does, the fault is isolated to the steering column stalk circuit rather than the transmission itself.

2. 2

   Physical Inspection: Check the S079 forward/reverse shuttle switch on the steering column for physical damage, sticking buttons, or debris.

3. 3

   Check Steering Adjustments: Inspect the quick reverse mechanism on the steering wheel adjustment, as mechanical binding can cause plausibility errors.

4. 4

   Wiring and Connectors: Inspect the wiring harness and separation points associated with the S079 switch (specifically separation points X1590 and X1591 located on the left side of the steering column) for loose connections, corrosion, or broken wires.

1. 1

   Preparation

   Turn off the tractor and disconnect the battery to ensure safety while working on the electrical system.

2. 2

   Access the Switch

   Remove the steering column covers to access the S079 control stalk switch assembly and its wiring connectors (X1590/X1591).

3. 3

   Disconnect and Test

   Disconnect the wiring harness from the S079 switch. Using a multimeter, test the switch for continuity according to the transmission control circuit diagram (Sheet 6) to confirm if the internal contacts for the forward travel signal have failed.

4. 4

   Replace the Switch

   If the switch fails the continuity test or is physically broken, unbolt and remove the faulty control stalk from the steering column. Install the new steering column/quick reverse switch and reconnect the wiring harness.

5. 5

   Reassembly

   Reinstall the steering column covers.

6. 6

   Clear Codes

   Reconnect the battery, turn on the tractor, and use the tractor's terminal or the FENDIAS diagnostic tool to clear the stored 04.1.2D fault code.

7. 7

   Operational Test

   Test the forward and reverse shuttle functions on the stalk to ensure the TMS remains active and the fault code does not return.