Massey Ferguson 3226.19 – Engine Control Unit (ECU): NOx Sensor Outlet SCR Signal Issue

The engine's control system has lost communication with the downstream (outlet) Nitrogen Oxide (NOx) sensor, or the signal being received is entirely implausible/missing. This critical emissions-related fault will typically trigger an engine derate after a defined time limit.

• 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
• 5611
• 5612
• 5613
• 5709
• 5710
• 5711
• 5712
• 5713
• 6612
• 6613
• 6614
• 6615
• 6616
• 8727
• 8730
• 8732
• 8735
• 8737
• 8740

1. 1

   Clear the error log using a diagnostic tool, restart the ECU, and cycle the key to see if the fault returns

2. 2

   Physically inspect the wiring harness leading to the downstream NOx sensor, checking connectors and pin contact surfaces for oxidation, corrosion, or physical damage

3. 3

   Monitor live data with a diagnostic tool to compare sensor data; if the downstream NOx reading is completely flat or implausible while the upstream NOx sensor responds normally to engine load, the downstream sensor is faulty

4. 4

   Plug in a known good test NOx sensor to verify if communication is restored before permanently installing a new one

1. 1

   Preparation

   Turn off the tractor, remove the key, and allow the exhaust system to cool completely. Disconnect the battery to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the downstream NOx sensor, which is installed directly into the exhaust pipe downstream of the Selective Catalytic Reduction (SCR) catalyst.

3. 3

   Removal

   Disconnect the 5-pin electrical connector. Carefully unthread the sensor from the exhaust pipe.

4. 4

   Installation Precautions

   Do not touch the ceramic probe of the new sensor with your bare fingers, as oil contamination will cause premature failure. Do not use an impact wrench to install the sensor, as this will damage the threads and void the warranty.

5. 5

   Install the New Sensor

   Thread the new sensor into the exhaust pipe using a new sealing washer. Tighten to the manufacturer's specified torque.

6. 6

   Reconnect

   Plug in the electrical connector and ensure it clicks securely into place.

7. 7

   Clear Codes

   Reconnect the battery, turn on the ignition, and use a diagnostic tool to clear the 003226.19 fault code. Run the tractor through a drive cycle to ensure the code does not return.