Fendt A.1.4A – ECU, enhanced control (electric auxiliary control valves) / A002: Spool valve fault, valve 4: Main piston is deflected too far

The main piston of the auxiliary control valve (Valve 4 / Position 4) is deflected too far. The system forces the valve into the neutral position and locks it to prevent further damage or unintended hydraulic operation. This is frequently caused by hydraulic oil contamination preventing the main piston from returning to neutral, or an internal mechanical/actuator failure.

• 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) / Favorit 700
• Fendt 800 Vario (COM III)
• Fendt 900 Vario (COM III) / Favorit 900 (including 916, 920, 924, 926, 930 Vario)

1. 1

   Inspect the hydraulic oil for debris or heavy contamination (primary cause of the spool valve piston sticking or deflecting improperly)

2. 2

   Test the control pressure at port M5 (ensure it does not drop below 22 bar) to rule out pressure-related erratic piston travel

3. 3

   Check the diaphragm accumulator and RV7/FP valve to ensure the hydraulic pilot circuit is maintaining proper pressure

4. 4

   Verify the supply voltage to the valve (should be between 8V and 18V) to rule out electrical default to neutral

1. 1

   Relieve Pressure

   Ensure the tractor is off, the engine is in idle (if testing), and all hydraulic pressure is relieved. Valves and EPC must be locked.

2. 2

   Locate Valve Y018

   Locate the auxiliary control valve block. Y018 is Position 4, which is color-coded green.

3. 3

   Clean and Inspect

   Remove the Y018 valve. Inspect the main piston and the valve bore for scoring, metal shavings, or debris.

4. 4

   Flush System

   If contamination is found, flush the hydraulic system and replace the hydraulic filters before installing a new valve to prevent immediate failure of the replacement part.

5. 5

   Replace the Valve

   If the piston is mechanically damaged, scored, or the internal actuator has failed, replace the entire Y018 auxiliary control valve.

6. 6

   EOL Programming

   Use FENDIAS to perform EOL programming and calibrate the linear module (Calibration code 1006 for Valve 4) so the ECU recognizes the new valve.