Massey Ferguson A.42.21 – Transmission Control Unit (TCU) or dedicated hydraulic valve control module: External Hydraulic Valve 4 Issue

Indicates a potential fault, connection problem, or pressure issue within the 4th external hydraulic remote valve (spool valve) circuit.

• 5710SL
• 5711SL
• 5712SL
• 5713SL
• T4
• 4707
• 4708
• 4709
• 4710
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 7714
• 7715
• 7715S
• 7716
• 7716S
• 7718
• 7718S
• 7719
• 7720
• 7720S
• 7722
• 7722S
• 7724
• 7724S
• 7726
• 7726S
• 8600 Series

1. 1

   Check the hydraulic fluid level and condition (look for dark, burnt, or milky appearance indicating water contamination or loss of viscosity)

2. 2

   Inspect the hydraulic filter for partial blockages that could restrict flow to the system

3. 3

   Perform a system pressure test with a hydraulic gauge to pinpoint whether the issue is isolated to Valve 4, the pump, or a general restriction

4. 4

   Inspect the external hydraulic valve block, fittings, and couplers for slow seeps or leaks that rob the system of pressure

5. 5

   Check the wiring harness and connectors leading to Solenoid Valve 4 for open circuits, short circuits to earth, or short circuits between cables

1. 1

   Fluid and Filter Service

   If the hydraulic fluid is degraded or contaminated, drain the system, replace the hydraulic filter, and refill with fresh UTTO fluid.

2. 2

   Unstick the Valve

   If the control valve is physically stuck, you can sometimes release it by manually moving the pump control valve lever back and forth.

3. 3

   Electrical Repair

   If the diagnostic checks revealed a wiring issue (e.g., a connection problem on the hydraulic valve), repair or replace the damaged wiring harness section leading to the 4th remote valve.

4. 4

   Solenoid Replacement

   If the wiring is intact but the valve fails to actuate, the solenoid coil on Valve 4 is likely burnt out. Remove the retaining nut, slide off the old solenoid, and install a new OEM solenoid.

5. 5

   Valve Block Overhaul/Replacement

   If the valve chamber is not sealing internally (causing pressure loss or implement dropping), remove the external hydraulic valve assembly. Clean the valve spool, replace the internal O-rings/seals, or replace the entire valve block if it is heavily scored.

6. 6

   Clear Codes

   Once the repair is complete, use a compatible Massey Ferguson diagnostic tool to clear the 0A.42.21 code from the system.