Fendt 05.1.B2 – A050 - ECU, basic control unit: Plausibility error with S075 - Switch, guard rail pump flow monitor

The flow monitor is reporting a guard rail pump failure or an implausible voltage state. The system expects that when the tractor is stationary and during reverse travel, the signal voltage (u) from the switch must be < 1.1 V. If the voltage does not drop below this threshold during these states, the 05.1.B2 code is logged.

• 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 300 Vario
• Fendt 400 Vario
• Fendt 500 Vario
• Fendt 700 Vario
• Fendt 800 Vario
• Fendt 900 Vario
• 922
• 924
• 927
• 930
• 933
• 936
• 939

1. 1

   Verify the A050 basic control unit is supplying the correct 6.0 VDC reference voltage to the S075 switch.

2. 2

   Monitor the S075 switch signal voltage; it must be < 1.1 V when stationary or in reverse.

3. 3

   Check the switch output voltage during forward travel (> 16 km/h); it must rise to > 1.1 V.

4. 4

   Inspect separation point X1499 at the central valve block for loose pins, corrosion, or wiring damage.

1. 1

   Park the tractor on a level surface, turn off the engine, apply the handbrake, and ensure all hydraulic pressure is relieved.

   Park the tractor on a level surface, turn off the engine, apply the handbrake, and ensure all hydraulic pressure is relieved.

2. 2

   Access the right side of the tractor and remove the cover for the central valve block to locate the S075 switch and its wiring harness.

   Access the right side of the tractor and remove the cover for the central valve block to locate the S075 switch and its wiring harness.

3. 3

   Disconnect the harness at separation point X1499. Inspect the connector for moisture, corrosion, or backed-out pins. Clean and repair the connector if necessary.

   Disconnect the harness at separation point X1499. Inspect the connector for moisture, corrosion, or backed-out pins. Clean and repair the connector if necessary.

4. 4

   Using a multimeter, test the continuity of the wiring between X1499, the S075 switch, and the A050 ECU.

   Using a multimeter, test the continuity of the wiring between X1499, the S075 switch, and the A050 ECU.

5. 5

   If the wiring is intact and the ECU is providing the 6.0 VDC reference voltage, but the switch fails to toggle its output voltage correctly based on the tractor's movement state (< 1.1 V stationary/reverse; > 1.1 V forward >16km/h), the S075 switch has failed internally.

   If the wiring is intact and the ECU is providing the 6.0 VDC reference voltage, but the switch fails to toggle its output voltage correctly based on the tractor's movement state (< 1.1 V stationary/reverse; > 1.1 V forward >16km/h), the S075 switch has failed internally.

6. 6

   Unthread and remove the faulty S075 guard rail pump flow monitor switch from the hydraulic block.

   Unthread and remove the faulty S075 guard rail pump flow monitor switch from the hydraulic block.

7. 7

   Install the replacement switch and torque to OEM specifications. Reconnect the X1499 wiring harness.

   Install the replacement switch and torque to OEM specifications. Reconnect the X1499 wiring harness.

8. 8

   Clear the stored 05.1.B2 fault code using the tractor's terminal or the FENDIAS diagnostic tool, then test drive the tractor in forward and reverse to ensure the code does not return.

   Clear the stored 05.1.B2 fault code using the tractor's terminal or the FENDIAS diagnostic tool, then test drive the tractor in forward and reverse to ensure the code does not return.