Fendt 5.1.9B – E-box: Electrical interruption (open circuit) involving S025 and/or S026

The system detects an electrical interruption (open circuit) between the sensor connector and the E-box, or between the connector and the flow controller. This results in a complete loss of pressure and flow monitoring for the hydraulic pumps, which can cause the control valve flow to be automatically reduced.

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1. 1

   Verify if the fault code is present immediately at 'Ignition ON' or only when the engine is running

2. 2

   Inspect the wiring harness and connectors for the S025 and S026 sensors for physical disconnections, breaks, or corrosion

3. 3

   Locate the S025 (8 bar pressure switch) at the right entrance step and S026 (flow monitor) on the right side of the engine

4. 4

   Perform a voltage test on the signal lines (expected test sequence voltage is 0 / 8 V, or a constant 8 V if tested before ignition)

5. 5

   Consult the 'Spool valves 1' circuit diagram to trace the wiring path from the sensors back to the E-box

1. 1

   Turn off the tractor and ensure the ignition is completely off.

   Ensure the machine is powered down before beginning work.

2. 2

   Access the S025 pressure switch and S026 flow monitor.

   S025 is located at the right entrance step on top of the central control valve block. S026 is located on the right side of the engine.

3. 3

   Disconnect the connectors for both sensors and inspect.

   Inspect the pins for damage, pushed-out terminals, or corrosion. Clean and reseat if necessary.

4. 4

   Test the continuity of the wiring harness.

   Check between the sensor connectors and the E-box. Repair any broken or chafed wires that are causing the interruption.

5. 5

   Replace the faulty sensor(s) if wiring is intact.

   If the wiring is intact and the voltage readings are correct at the connector (8 V), the fault likely lies within the sensor(s) failing internally. Replace the faulty S025 8-bar pressure switch or S026 flow monitor.

6. 6

   Reconnect all components securely.

   Ensure all connections are tight and replace any removed metal panels.

7. 7

   Turn the ignition on and clear the fault codes.

   Note: The fault code can be cancelled via the terminal, but if the underlying open circuit is not resolved, it will reappear after 10 minutes or upon restarting the tractor.

8. 8

   Start the engine and verify operation.

   Verify that the hydraulic spool valves operate correctly and that flow is no longer being automatically restricted.