Fendt 04.1.2E – Transmission Control System: S079 - Switch, steering column "Quick reverse" button on control stalk

Faulty reverse travel signal coming from the forward/reverse shuttle switch on the steering column, causing the TMS (Tractor Management System) to be switched off.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• 300 Vario (309, 310, 311, 312)
• 400 Vario (409, 410, 411, 412)
• 700 Vario (711, 712, 714, 716)
• 800 Vario (815, 817, 818, 820)
• 900 Vario (916, 920, 922, 924, 926, 927, 930, 933, 936)

1. 1

   Locate the electrical separation points/connectors X1590 and X1591 for the S079 switch on the left side of the steering column inside the cab

2. 2

   Inspect the wiring harness between the steering column switch and the ECU for breaks, chafing, or short circuits

3. 3

   Measure the signal voltage and resistance at pins 1 and 2 of the switch with it open (should be infinite resistance and approx. 6.1 VDC for A050 ECU or 8.0 VDC for A002 ECU)

4. 4

   Measure the signal voltage and resistance at pins 1 and 2 of the switch with it closed (should be approx. 0 ohms and 0 VDC)

1. 1

   Secure the tractor

   Park the tractor safely, turn off the ignition, and engage the handbrake.

2. 2

   Remove steering column covers

   Remove the plastic cowlings/covers on the left side of the steering column to access the S079 switch assembly.

3. 3

   Disconnect wiring

   Disconnect the X1590 and X1591 wiring connectors.

4. 4

   Test the switch

   Perform the multimeter tests outlined in the diagnostic section.

5. 5

   Evaluate switch condition

   If the switch fails the resistance or voltage drop tests (e.g., it stays open when pressed or shows high resistance when closed), the S079 switch stalk has internally failed and must be replaced.

6. 6

   Remove faulty switch

   Unbolt/unclip the faulty S079 steering column switch from the steering wheel adjustment mechanism.

7. 7

   Install new switch

   Install the new genuine Fendt steering column switch and reconnect the X1590 and X1591 connectors.

8. 8

   Reinstall covers

   Reinstall the steering column covers.

9. 9

   Clear codes and test

   Turn on the tractor, clear the stored 04.1.2E fault code from the terminal memory, and test the quick reverse function to ensure the TMS system engages properly.