Massey Ferguson 520337.31 – Engine Control Unit (ECU): Fuel Rail Pressure High. Engine Derate Active.

The system has detected that the fuel rail pressure has exceeded the maximum allowable limit (overpressure). To protect the engine and fuel system components from catastrophic damage, the system actively limits the engine torque and power (Engine Derate Active / Limp Mode).

• 4710
• 7724S
• 5712SL
• 7722S
• 7722
• 5713SL
• 7720S
• 7716
• 7718
• T4
• 7715
• 5710SL
• 7726
• 4708
• 7726S
• 4707
• 4709
• 5711SL
• 7718S
• 7719
• 7714
• 7716S
• T4 (2015-2021)
• 7720
• Tier 4 (2015-2021)
• 7715S
• 7724
• 4700 Series
• 5600 Series
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 7600 Series
• 7700 Series
• 7614-7626
• 8700 Series
• T Series CVT Tractors

1. 1

   Connect a diagnostic tool to read live data and compare the commanded fuel rail pressure against the actual fuel rail pressure

2. 2

   Inspect the wiring harness and connectors for both the Fuel Rail Pressure Sensor and the Fuel Rail Pressure Control Valve for shorts to ground, shorts to power (+12V), or open circuits

3. 3

   Check the fuel return lines for kinks, blockages, or restrictions (a blocked return line will cause pressure to build up in the rail)

4. 4

   Perform a hysteresis test on the fuel rail pressure control valve using the diagnostic tool to see if the valve is sticking

1. 1

   Relieve Pressure

   Ensure the engine is off and the high-pressure fuel system has had time to depressurize before opening any lines.

2. 2

   Inspect/Replace the Control Valve

   If the wiring is intact and the return lines are clear, remove and replace the control valve on the high-pressure pump/rail. High pressure is most commonly caused by a Fuel Rail Pressure Control Valve that is stuck closed.

3. 3

   Inspect/Replace the Sensor

   If the mechanical pressure is normal but the ECU is receiving a false high reading, the Fuel Rail Pressure Sensor is faulty. Replace the sensor.

4. 4

   Reassemble and Bleed

   Reinstall the components, torque to OEM specifications, and prime the fuel system to remove any air.

5. 5

   Clear Codes

   Use the diagnostic tool to clear the 520337.31 fault code and test run the engine to ensure the derate is lifted and pressure remains within normal operating limits.