Massey Ferguson 520312.31 – Engine ECU: Fuel Rail Pressure High / Rail Pressure control: Maximum time in limp home state is exceeded

The common rail fuel system has experienced critically high pressure, triggering an over-pressure protection mode. Because the system has been operating in this restricted "limp home" state longer than the maximum allowed time, the controller logs this specific code.

• 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
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 7714S
• 7719S

1. 1

   Check for companion codes: Look for related active fault codes that confirm the over-pressure event, such as 520307.31 (Pressure ABOVE measurable range), 520388.31 (Over pressure protection mode activated), or 520327.31 (Pressure ABOVE NORMAL)

2. 2

   Live data monitoring: Use a diagnostic tool to monitor actual vs. desired fuel rail pressure while the engine is running to see if the sensor is reading falsely high or if the pump is actually over-pressurizing the rail

3. 3

   Wiring inspection: Inspect the wiring harness and connectors at the Fuel Rail Pressure Sensor and the Fuel Pressure Control Valve (on the high-pressure pump) for shorts, corrosion, or open circuits

4. 4

   Relief valve check: Check the mechanical Fuel Rail Pressure Relief Valve (pop-off valve). If the system actually over-pressurized, this valve may have opened to protect the system and might now be weakened or leaking

1. 1

   Depressurize the System

   Ensure the engine is off and relieve the fuel system pressure before opening any high-pressure lines.

2. 2

   Address Electrical Faults

   Clean and secure the electrical connections to the fuel rail pressure sensor and the fuel pressure control valve.

3. 3

   Replace the Sensor (If Falsely High)

   If diagnostics show the sensor is reading out of range or falsely high, replace the Fuel Rail Pressure Sensor on the fuel rail.

4. 4

   Replace the Control Valve (If Actually High)

   If the system is genuinely over-pressurizing, replace the Fuel Pressure Control Valve (suction control valve) located on the high-pressure fuel pump. A sticking valve will cause runaway rail pressure.

5. 5

   Replace the Relief Valve

   If the system experienced a severe over-pressure event, the mechanical Fuel Rail Pressure Relief Valve (limiter valve) on the rail likely "popped." It is highly recommended to replace it, as it can weaken after opening and cause low-pressure limp modes later.

6. 6

   Clear and Test

   Bleed the fuel system, clear the ECU fault codes using a diagnostic tool, and test run the tractor under load to verify the rail pressure matches the commanded pressure.