Massey Ferguson 520359.03 – Engine ECU: Open load of pressure control valve output

The engine control module has detected an electrical fault (open circuit, short circuit to the battery, or internal ECU driver over-temperature) on the circuit that commands the Fuel Rail Pressure Control Valve. Because the ECU cannot control this valve, it cannot properly regulate the high-pressure fuel rail, which typically forces the engine into a derated power state.

• 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 7700 series
• Tractors and combines equipped with AGCO Power (Sisu) Tier 3 and Tier 4 engines

1. 1

   Inspect the wiring harness and connector between the Engine ECU and the Fuel Rail Pressure Control Valve for chafing, shorts to battery/ground, corrosion, backed-out pins, or moisture

2. 2

   Measure the resistance across the pins of the Fuel Rail Pressure Control Valve to check for an internal open circuit in the solenoid coil

3. 3

   Perform the ECU internal driver check: erase the fault code and operate the vehicle for a short distance to see if the error reappears immediately

1. 1

   Disconnect Power

   Disconnect the machine's battery before servicing the fuel system or ECU.

2. 2

   Harness Repair

   If the diagnostic checks revealed broken or shorted wires between the ECU and the valve, repair the wiring harness or replace the damaged connector pigtail.

3. 3

   Valve Replacement

   If the wiring is intact but the Fuel Rail Pressure Control Valve failed the resistance test, remove the defective valve from the high-pressure fuel pump and install a new one. Lubricate the O-rings on the new valve with clean diesel fuel before installation to prevent tearing.

4. 4

   ECU Replacement

   If the wiring and the valve are both in good working order, but the code immediately returns after clearing (indicating the ECU's internal driver is burnt out), the Engine ECU must be replaced and flashed with the correct software for the machine.

5. 5

   Clear and Verify

   Reconnect the battery, clear the inactive fault codes using a diagnostic tool, and run the engine to verify that rail pressure is regulating normally and the code does not return.