Fendt A.1.91 – A057 - ECU, steering controller (Autoguide): Short circuit in the steering valve block voltage supply earth

The ground/earth circuit providing voltage to the Autoguide steering valve block (Y087) has shorted out, preventing the steering controller from properly operating the valve.

• 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 820 Vario
• FENDT 900 Vario (COM III)

1. 1

   Consult Wiring Diagram Sheet 38 / 39 for the Autoguide steering valve electrical supply lines.

2. 2

   Use a multimeter to test the voltage supply earth line to the Y087 steering valve block for a short circuit to ground.

3. 3

   Inspect the electrical connectors at the steering valve block (separation points X1588 and X1589 on the 900 Vario). Look for pinched wires, rubbed insulation, or moisture ingress causing the short.

4. 4

   Check the supply voltage to the bus consumers. Test the total resistance of the passive bus system (should be 60 Ohms; 120 Ohms indicates a wiring break or defective terminating resistor). Check the voltage level of CAN High/CAN Low (0 VDC = earth connection, 4 VDC and higher = short circuit to +).

1. 1

   Access the Steering Valve Block (Y087)

   Safely support the tractor and remove the right rear wheel and panel to access the electro-hydraulic steering valve block located on the right side of the transmission.

2. 2

   Inspect and Repair Wiring

   Trace the wiring harness from the Y087 valve block back toward the A057 ECU. Locate the short circuit in the earth supply line. Repair any damaged wires or replace the affected harness section.

3. 3

   Test the Valve Block

   If the wiring harness is intact, check for an internal short in the Y087 steering valve block's solenoids or position sensor. If an internal short is confirmed, replace the steering valve block (or the specific steering head/actuator).

4. 4

   Reassembly

   Reconnect all separation points (X1588/X1589) and reinstall the right rear wheel and panel.

5. 5

   Recalibration

   After repairing the wiring or replacing the valve, enter calibration mode and run Calibration code "2403" (Steering valve calibration).