Massey Ferguson A.43.20 – Tractor Control Unit (TCU) or Hydraulic Control Module: External Hydraulic Valve 4 Issue

Malfunction in the electro-hydraulic circuit controlling the #4 rear remote spool valve. The system has detected an electrical anomaly—such as an open circuit, a short to ground, a short to power, or a current level error—preventing the valve from operating correctly.

• 5710SL
• 5711SL
• 5712SL
• 5713SL
• T4
• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7626
• 7714
• 7726S
• 8600 Series

1. 1

   Verify the hydraulic fluid (UTTO) is at the correct level and check its condition (look for dark, burnt, or milky fluid indicating water contamination)

2. 2

   Inspect the wiring harness leading to the #4 external hydraulic valve solenoid at the rear remote stack for rub points, pinched wires, or melted insulation

3. 3

   Disconnect the solenoid connector for Valve 4 and check for water ingress, corrosion, or loose pins

4. 4

   Test the solenoid coil resistance with a multimeter to check for an internal open circuit or short, and check the ground integrity of the circuit

5. 5

   If the electrical circuit passes, test the system pressure with a hydraulic gauge to ensure the pump and relief valves are functioning properly

1. 1

   Resolve Fluid Issues

   If the hydraulic fluid is contaminated, drain the system, replace the hydraulic filter, and refill with fresh OEM-spec UTTO fluid.

2. 2

   Repair Wiring

   If the diagnostic checks revealed a broken wire or corroded connector at the valve harness, splice in a new connector pigtail or repair the wire, ensuring it is sealed against moisture.

3. 3

   Replace the Solenoid/Valve

   If the solenoid coil fails the resistance test (indicating an internal short or open circuit), remove the retaining nut on the #4 spool valve and slide the old solenoid off. Install the new solenoid. If the mechanical spool itself is seized and cannot be freed, the entire valve section may need to be replaced.

4. 4

   Clear the Code

   Reconnect the battery (if disconnected) and use a compatible Massey Ferguson diagnostic tool (like the WinEEM or AGCO diagnostic interface) to clear the 0A.43.20 code from the TCU memory.

5. 5

   Test Operation

   Start the tractor, allow the hydraulic fluid to warm up, and actuate the #4 remote lever/button to ensure smooth operation and verify the code does not return.