Fendt 04.1.21 – A050 - ECU, basic control unit: S045 - Switch, reversing driver stand

The fault indicates a signal failure or faulty switch. The S045 switch is responsible for transmitting the position of the operator platform (whether the driver seat is facing forwards or backwards) to the control unit. When this fault is active, the system cannot reliably determine the seat position, which typically causes the ECU to limit the maximum reversing speed to 33 km/h and restricts joystick actuation directions for safety.

• 922 Vario COM III
• 924 Vario COM III
• 927 Vario COM III
• 930 Vario COM III
• 933 Vario COM III
• 936 Vario COM III
• Fendt Farmer 400 series
• Fendt Favorit 700 series
• Fendt Favorit 900 series
• Fendt 300 Vario series
• Fendt 400 Vario series
• Fendt 700 Vario series
• Fendt 800 Vario series
• Fendt 900 Vario series
• 922 Vario
• 924 Vario
• 927 Vario
• 930 Vario
• 933 Vario
• 936 Vario
• 939 Vario

1. 1

   Locate the S045 switch and its separation point (connector X213) inside the cab, below the rear window.

2. 2

   Perform a voltage test: Turn the ignition ON and measure the signal voltage at Pin 9 (X1402) with Earth at Pin 45 (X1403). With the driver seat facing forwards, the reading should be between 3.7 VDC and 6.1 VDC. With the driver seat facing backwards, the reading should drop to approximately 1.8 VDC.

3. 3

   Inspect the wiring harness between the S045 switch and the A050 ECU for open circuits, shorts to ground, or damaged pins at connector X213 if the voltage reads 0 VDC or is out of specification.

1. 1

   Power Down

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

2. 2

   Access the Switch

   Inside the cab, access the area below the rear window where the reversing driver stand pivot mechanism and the S045 switch are located.

3. 3

   Disconnect and Inspect

   Disconnect the X213 separation point connector. Inspect the terminals for corrosion, moisture, or pushed-out pins. Clean with contact cleaner if necessary.

4. 4

   Replace the Switch

   If the switch failed the multimeter voltage test (internal failure), unbolt the faulty S045 switch from its mounting bracket. Install the new switch and ensure it is properly aligned with the seat pivot mechanism so it actuates correctly when the seat is reversed.

5. 5

   Reconnect and Reassemble

   Plug the X213 connector back in and restore battery power.

6. 6

   Clear Codes and Test

   Turn the ignition ON. Rotate the driver stand from the forward to the reverse position and verify that the tractor registers the change without throwing the 04.1.21 code. Clear any stored historical codes using the tractor's terminal or the FENDIAS diagnostic tool.