Massey Ferguson E4090.18 – Engine ECU (AGCO SISU POWER EEM4): NOx Are High In The Exhaust

The engine management system has detected that the Nitrogen Oxide (NOx) emissions leaving the Selective Catalytic Reduction (SCR) catalyst are higher than expected or implausible. This typically indicates that the exhaust aftertreatment system is not effectively neutralizing NOx, which can be caused by poor DEF/AdBlue quality, a blocked DEF doser, or a failing NOx sensor.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 4707
• MF 4708
• MF 4709
• MF 4710
• MF 5608
• MF 5609
• MF 5610
• MF 5611
• MF 5612
• MF 5613
• MF 5710 SL
• MF 5711 SL
• MF 5712 SL
• MF 5713 SL
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 7619
• MF 7620
• MF 7622
• MF 7624
• MF 7626
• MF 7714
• MF 7715
• MF 7716
• MF 7718
• MF 7719
• MF 7720
• MF 7722
• MF 7724
• MF 7726

1. 1

   Test DEF/AdBlue quality using a refractometer to ensure it is exactly 32.5% urea concentration (poor fluid quality is the most common cause)

2. 2

   Visually inspect the DEF dosing pump, lines, and injector/doser nozzle in the exhaust for leaks, blockages, or crystallized urea deposits

3. 3

   Inspect the NOx sensor wiring harness and connectors for physical damage, melted wires, or corroded pins

1. 1

   Address Fluid Quality

   If the DEF fluid tests poorly (diluted, contaminated, or degraded), drain the DEF tank completely. Flush the tank and lines with warm distilled water, and refill with fresh, certified DEF.

2. 2

   Clean the Dosing System

   If you suspect a blockage, remove the DEF doser from the exhaust pipe. If crystallized urea is present, clean the nozzle carefully using a lint-free cloth and hot water. (Note: Do not use diesel fuel, oil, or hydrocarbon-based solvents to clean the DNOX2.2 dosing system, as it will cause permanent damage).

3. 3

   Replace the NOx Sensor

   If the DEF fluid is good, the doser is spraying correctly, and the wiring is intact, the NOx sensor itself has likely failed and is sending implausible readings to the EEM4 controller. Remove the old sensor from the exhaust and install the replacement.

4. 4

   Clear Codes and Test

   Connect an AGCO diagnostic tool (EEM4 Service Tool) to clear the E4090.18 / SPN 4090 fault code. Run the tractor under load to initiate a dosing cycle and verify the code does not return.