Massey Ferguson U 520201 – Engine ECU: Monitoring of Supply Module temperature

Malfunction in the temperature monitoring circuit of the DEF (Diesel Exhaust Fluid) / AdBlue Supply Module within the SCR (Selective Catalytic Reduction) emissions system.

• 8600 Series
• MF 8690
• 7600 Series
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• 6700 S Series

1. 1

   Visually inspect the DEF Supply Module and its electrical connector for DEF crystallization, moisture ingress, or pushed-back pins

2. 2

   Trace and inspect the wiring harness from the Supply Module to the Engine ECU for chafing, pinched wires, or melted insulation causing shorts to ground or battery

3. 3

   Test the temperature sensor and heater circuits for continuity using a multimeter (Engine ECU pins: K24 for 5V reference, K78 for analog signal, K77 for ground)

4. 4

   Check for related fault codes, such as SPN 4344, which can isolate the failure to the module's internal heater or temperature sensor

1. 1

   Preparation

   Turn off the ignition, remove the key, and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Clean the Area

   Thoroughly clean the area around the DEF tank and Supply Module. The SCR system is highly sensitive to contamination; dirt or debris entering the system will cause further dosing faults.

3. 3

   Disconnect Lines

   Carefully disconnect the DEF supply and return lines from the module. Cap the lines immediately to prevent fluid leakage and contamination.

4. 4

   Disconnect Electricals

   Unplug the main electrical harness connector from the Supply Module.

5. 5

   Remove the Module

   Unbolt the faulty DEF Supply Module from its mounting bracket on the tank.

6. 6

   Install the New Module

   Mount the replacement Supply Module. Reconnect the fluid lines, ensuring the O-rings are intact and the quick-connectors click securely into place to prevent air ingress.

7. 7

   Reconnect Electricals

   Plug in the electrical connector, ensuring it is fully seated and locked.

8. 8

   System Prime and Clear

   Reconnect the battery. Turn the ignition on. Use a diagnostic service tool (such as the WinEEM4 Service Tool) to clear the U 520201 fault code. The system will need to prime to purge air from the fluid lines before normal operation resumes.