Massey Ferguson U 1677 – Engine Control Unit (ECU) / EEM: Modular Heater State Machine Error

The SCR/DEF system failed to thaw the lines or build pressure, meaning the DEF remains frozen or the heater circuit has failed.

• Massey Ferguson 8600 Series
• MF 8650
• MF 8660
• MF 8670
• MF 8680
• MF 8690
• Massey Ferguson 8700 Series
• Massey Ferguson 8700 S Series

1. 1

   Check DEF quality and level to ensure the tank is adequately filled and fluid is not contaminated with water or diesel.

2. 2

   Visually inspect the DEF inlet, pressure, and backflow lines for physical damage, kinks, or severe rub points, and ensure quick-connect fittings are fully seated.

3. 3

   Test the DEF supply module heater relay and line heater relays for open circuits or shorts, checking for related relay fault codes like U 1485 or SPN 4356/4357.

4. 4

   Disconnect the electrical connectors for the specific DEF line indicated by the FMI and use a multimeter to check the resistance of the internal heating element.

1. 1

   Clear the Error Log

   Connect the diagnostic service tool (e.g., WinEEM3/EEM4 tool), save the error log, and erase the active codes.

2. 2

   Isolate the Faulty Component

   Based on the continuity test, determine if the failure is in the wiring harness, the relay, the heated line, or the main DEF supply module.

3. 3

   Replace the Defective Line/Module

   If a specific line (inlet, pressure, or backflow) fails the resistance test, depressurize the system, disconnect the quick-connect fluid fittings and electrical harness, and route a new OEM heated line. If the main supply module heater is defective, remove the DEF supply module from the tank assembly and install a replacement unit.

4. 4

   Reassemble and Prime

   Reconnect all fluid lines, ensuring O-rings are lubricated and seated correctly to prevent air leaks.

5. 5

   System Reset

   Restart the ECU (cycle the ignition). The system will run a self-test on the heater state machine. Verify that the warning lamp turns off and the engine is no longer in a derated power state.