Massey Ferguson 520318.31 – Engine ECU: There Is A Problem With The Fuel Rail Pressure When The Tractor Is In Limp Mode Or Active Derate

The engine control system has detected that the fuel rail pressure is deviating from the expected or commanded parameters while the engine is already operating in a derated state (limp home mode). The FMI 31 identifier indicates an out-of-range or unreliable sensor signal.

• 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
• MF 3600 Series
• MF 5400 Series
• MF 6400 Series
• MF 7400 Series
• MF 8400 Series
• MF 8600 Series
• MF 4700 Series
• MF 5700 Series
• MF 2600H Series
• 2604H
• 2605H
• 2606H

1. 1

   Check for primary codes: Since this code triggers when the tractor is in limp mode, check the ECU for other active fault codes that caused the engine to derate initially.

2. 2

   Inspect the wiring harness between the fuel rail pressure sensor and the Engine ECU for shorts, open circuits, loose connectors, or corrosion.

3. 3

   Inspect the fuel system to verify there are no physical blockages in the fuel lines, fuel filters are clean, and the high-pressure fuel pump is operating correctly.

4. 4

   Test the fuel rail pressure sensor for physical damage or erratic voltage signals.

1. 1

   Connect Diagnostic Tool

   Connect a compatible diagnostic scanner to the tractor's OBD/CAN port to read all active and stored DTCs.

2. 2

   Address Primary Faults

   Diagnose and repair any primary codes that forced the tractor into Limp Mode. Clearing the primary issue often resolves secondary deviation codes like 520318.31.

3. 3

   Perform Electrical Testing

   Disconnect the fuel rail pressure sensor. Use a multimeter to verify that the sensor is receiving the correct reference voltage and ground from the ECU.

4. 4

   Clean Connections

   If the wiring is intact but the signal is unreliable, clean the sensor connector pins with electrical contact cleaner and ensure a tight fit.

5. 5

   Replace the Sensor

   If the wiring tests good, the fuel system is unobstructed, and the code persists (or the sensor fails electrical resistance testing), replace the fuel rail pressure sensor.

6. 6

   Clear Codes and Test

   Use the diagnostic tool to clear the DTCs from the Engine ECU. Run the tractor under load to ensure the fuel rail pressure remains within the commanded range and the limp mode does not return.