Massey Ferguson 520208.31 – Engine Control Unit (ECU) / EEM4: Rail PRV recognised as OPEN

The fuel rail pressure relief valve (PRV) has been forced open and is remaining open. When this code is active, engine functions dependent on rail pressure are deactivated to protect the system.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 7600 Series
• 5600 Series
• 6700 Series
• Dyna-4
• Dyna-6

1. 1

   Save the error log, erase it, and restart the ECU.

2. 2

   Run the tractor through a test cycle to see if the fault occurs again during the next driving cycle.

3. 3

   Check the injector solenoid valves' wiring, connectors, and the contact surfaces of the connector pins for possible oxidation.

4. 4

   Check the rail pressure sensor wiring for shorts or high resistance.

5. 5

   Measure the fuel leakage from the fuel rail pressure relief valve (if the engine will not start, perform this test while cranking). A leaking valve confirms it is stuck open.

1. 1

   Resolve Electrical Issues

   If oxidation or wiring damage was found during the diagnostic checks on the injector solenoids or pressure sensor, clean the pins with contact cleaner or repair the wiring harness.

2. 2

   Depressurize the System

   If the wiring is sound and the PRV is confirmed to be leaking/stuck open, turn off the engine and allow the high-pressure fuel system to depressurize completely.

3. 3

   Remove the PRV

   Locate the Fuel Rail Pressure Relief Valve on the common fuel rail. Disconnect the fuel return line attached to it, then unthread the valve from the rail.

4. 4

   Install the New Valve

   Thread the new PRV into the fuel rail and torque it to the exact specification outlined in your specific engine's service manual (over-tightening can damage the rail; under-tightening will cause high-pressure leaks).

5. 5

   Reassemble and Prime

   Reattach the fuel return line. Prime the fuel system to remove air.

6. 6

   Clear Codes and Test

   Connect your diagnostic tool, clear the 520208.31 code, and run the engine to verify that rail pressure normalizes and the code does not return.