Massey Ferguson 4095.31 – Engine Control Unit (ECU): NOx Are High In The Exhaust (ECU)

The engine's Selective Catalytic Reduction (SCR) aftertreatment system is failing to adequately reduce Nitrogen Oxide (NOx) emissions into harmless nitrogen and water vapor.

• 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
• 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• 7714S
• 7719S

1. 1

   DEF Quality Check: Test the Diesel Exhaust Fluid (DEF/AdBlue) concentration using a refractometer. The fluid must be a precise 32.5% urea solution. Contamination from dirt, water, or diesel fuel is a primary cause of SCR inefficiency.

2. 2

   Visual Inspection of the Doser: Inspect the DEF dosing injector (mounted in the exhaust stream) and the tailpipe. If the system fails to purge properly at shutdown, DEF can dry at the tip, causing white crystalline buildup. This distorts the spray pattern and triggers NOx efficiency codes.

3. 3

   NOx Sensor Data Comparison: A failing NOx sensor often mimics a DEF dosing issue. Use a diagnostic tool to compare the upstream (engine-out) and downstream (catalyst-out) NOx sensor readings under a steady load to verify if the catalyst is underperforming or if a sensor is reporting falsely.

4. 4

   Inspect DEF Lines: Check the heated DEF supply and return lines for kinks, rub points, or damaged O-rings at the quick connectors. Air ingress here can cause dosing errors.

1. 1

   Address Fluid Issues

   If the DEF is contaminated or diluted, drain the DEF tank completely, flush the system, and refill with fresh, high-quality DEF.

2. 2

   Clean or Replace the Doser

   Remove the DEF dosing injector. If white crystals are present, clean the injector tip. If the injector is damaged or fails a diagnostic dosing test, replace it.

3. 3

   Replace Faulty Sensors

   If diagnostic data proves the downstream NOx sensor is reading erratically or failing to measure accurately despite proper DEF dosing, replace the NOx sensor.

4. 4

   Reassemble and Seal

   Reinstall all components, ensuring that all DEF line quick-connectors and O-rings are perfectly seated to prevent air leaks.

5. 5

   Clear Codes and Test

   Connect a dealer diagnostic tool (such as WinEEM3s or WinEEM4) to clear the fault codes. Run the tractor under load or perform a forced SCR system test to verify that NOx conversion efficiency is restored and the code does not return.