Massey Ferguson U 2859 – Engine ECU: Urea / Heater or Exhaust Measurement State

CAN Frame Error indicating that the message from the SCR system regarding the DEF heating status, dosing status, or exhaust gas temperature/mass has been overridden or timed out. Machine enters emergency operation mode (derate), limiting engine power to 60% and maximum engine speed to 1500 RPM.

• 8600 Series
• 8650
• 8660
• 8670
• 8680
• 8690

1. 1

   Scan for Sub-Codes: Connect the Massey Ferguson EDT to check the specific FMI (FMI 2, 9, or 19) to isolate the fault.

2. 2

   Fluid Quality Check (Dosing/Quality cause): Verify the DEF/AdBlue fluid is a precise 32.5% urea solution and free of contamination.

3. 3

   Heater Circuit Inspection (Heating status cause): Check fuses and test the resistance of the three reductant heaters (reservoir, pump, lines).

4. 4

   Sensor Wiring Check (Exhaust temp/mass cause): Inspect wiring harnesses and connectors for the EGT and NOx sensors for melted wires, corrosion, or CAN bus breaks.

1. 1

   Isolate the Fault

   Use the EDT to determine if the U 2859 code is being triggered by the heating circuit, the dosing pump, or the exhaust temperature measurement.

2. 2

   Address Fluid/Filter Issues

   If the fluid is contaminated or degraded, drain the DEF tank completely. Flush the system and replace the DEF pump filter. Refill with fresh, high-quality AdBlue/DEF.

3. 3

   Test and Replace Heaters

   If the diagnostic tool points to a heating status error, use a multimeter to check the continuity of the DEF tank heater and heated lines. Replace any heater that shows an open circuit or short to ground.

4. 4

   Test and Replace Exhaust Sensors

   If the error points to 'Exh. gas mass or temp,' remove the exhaust gas temperature sensor from the exhaust pipe. Inspect it for heavy soot buildup or damage. Test its resistance at ambient temperature against OEM specs; replace the sensor if it is out of range.

5. 5

   Clear Codes and Regenerate

   After replacing the faulty component, reconnect the EDT diagnostic tool, clear the inactive U 2859 code, and perform a forced SCR system test or stationary regeneration to ensure the engine exits the 60% power derate mode.