Fendt A.1.84 – Steering Controller ECU (A057): S088 - Switch, Autoguide pressure

Short-circuit in the supply line of the pressure switch signal line.

• 411 Vario COM III
• 412 Vario COM III
• 413 Vario COM III
• 414 Vario COM III
• 415 Vario COM III
• 712 Vario COM III
• 714 Vario COM III
• 716 Vario COM III
• 718 Vario COM III
• 818 Vario COM III
• 820 Vario COM III
• FENDT 300 Vario (COM III)
• FENDT 400 Vario (COM III)
• FENDT 700 Vario (COM III)
• FENDT 800 Vario (COM III)
• FENDT 900 Vario (COM III)

1. 1

   Consult Wiring Diagram Sheet 39 for the Auto-Guide steering valve block and pressure switch circuits

2. 2

   Inspect the wiring harness leading to the S088 Auto-Guide pressure switch for chafing, pinched wires, or exposed copper that could cause a short circuit in the supply line

3. 3

   Use a multimeter to test the supply voltage and signal line continuity

4. 4

   Use the Auto-Guide COM III tool box (Part No. X899.980.316.000) and adapter cable X899.980.246.204 to isolate and test the S088 pressure switch circuit

1. 1

   Turn off the tractor and ensure the hydraulic system is depressurized.

2. 2

   Locate the S088 Auto-Guide pressure switch on the steering valve block (Y087).

3. 3

   Disconnect the electrical connector from the S088 switch.

4. 4

   Verify if the short circuit is present in the tractor-side wiring harness or internal to the switch itself.

   Use the adapter cable (X899.980.246.204) or a multimeter.

5. 5

   If the wiring harness is shorted: Trace the harness back to the Steering Controller ECU (A057) and repair the damaged section of the wire.

6. 6

   If the wiring is intact: Remove the faulty switch from the valve block.

   The S088 pressure switch has failed internally and is shorting the supply voltage.

7. 7

   Install the new Auto-Guide pressure switch and torque to OEM specifications.

8. 8

   Reconnect the electrical harness, start the tractor, and clear the stored fault codes.

   Use the terminal or FENDIAS diagnostic software.

9. 9

   Engage the Auto-Guide system to verify the repair.