Massey Ferguson E521006.12 – Engine ECU (EEM4): NOx sensor Common control error / NOx conversion implausible

The engine control system has detected that the Selective Catalytic Reduction (SCR) system is failing to reduce Nitrogen Oxide (NOx) emissions to acceptable levels. The system compares the expected NOx reduction against the actual readings from the NOx sensors, and the conversion rate is implausible or failing.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 4707
• 4708
• 4709
• 4710
• 5708
• 5709
• 5710
• 5711
• 5712
• 5713
• 6612-6616
• 6711-6718
• 7714-7726
• 8727-8740

1. 1

   Check DEF/AdBlue quality to ensure it is ISO 22241-compliant. Poor quality, diluted, or contaminated DEF is a primary cause of this code.

2. 2

   Inspect the DEF supply module main filter to see if it is blocked or heavily contaminated.

3. 3

   Inspect the DEF dosing valve (injector) and its mounting boss on the exhaust for crystallization or blockages.

4. 4

   Check the DEF pressure line and return line for blockages, kinks, or leaks.

5. 5

   Inspect the physical condition of the NOx sensors and ensure the wiring harnesses are routed correctly, free from heat soak damage or vibration chafing.

6. 6

   Evaluate the SCR catalyst to see if the DEF catalyst itself is deteriorated or blocked with soot/crystallized DEF.

1. 1

   Drain and Flush DEF (If Contaminated)

   If the DEF quality is suspect, drain the tank completely, flush it, and refill with fresh, high-quality AdBlue/DEF.

2. 2

   Replace the DEF Filter

   Remove the DEF supply module main filter/strainer and replace it with a new one (this is recommended every 12 months or 1,000 hours anyway). Replace the quick-connector O-rings if disturbed.

3. 3

   Clean/Replace the Dosing Valve

   Remove the DEF dosing valve from the exhaust mounting boss. Clean any crystallized DEF from the nozzle and the mounting boss. If the valve is mechanically failed or completely blocked, replace it and install a new doser gasket.

4. 4

   Clear Lines

   Use compressed air (carefully, following OEM pressure limits) to ensure the DEF pressure and return lines are clear of blockages.

5. 5

   Replace NOx Sensor (If Necessary)

   If DEF delivery is confirmed to be perfect and the code persists, the NOx sensor itself is likely providing false readings. Replace the faulty NOx sensor.

6. 6

   Clear Codes

   Reconnect diagnostic equipment to the EEM4 module, clear the active E521006.12 fault code, and run the tractor under load to verify the SCR system is actively reducing NOx.