Massey Ferguson 3228.14 – Engine Control Unit (ECU): Issue With Supply Voltage To NOx Sensor Outlet SCR

The Engine Control Unit has detected that the supply voltage to the downstream (outlet) NOx sensor is out of range. This sensor is responsible for measuring the nitrogen oxide levels in the exhaust gases after they pass through the Selective Catalytic Reduction (SCR) system to ensure the AdBlue/DEF injection is working correctly.

• 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
• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626

1. 1

   Check the fuse and relay assortment for the after-treatment circuits to rule out intermittent voltage drops or blown fuses.

2. 2

   Inspect the wiring harness routing to the downstream NOx sensor for signs of heat soak, melting, or vibration damage.

3. 3

   Use a multimeter at the NOx sensor connector to verify if the supply voltage is actually out of range or if the circuit is open.

4. 4

   Check the SCR outlet gasket and clamps for exhaust leaks, which can skew NOx readings and trigger plausibility faults.

5. 5

   Inspect the pins on the ECU and the sensor connector for corrosion, moisture, or poor contact.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to ensure safety and prevent short circuits during the repair.

2. 2

   Locate the Sensor

   Locate the downstream NOx sensor, which is positioned on the exhaust pipe after the SCR catalytic converter.

3. 3

   Disconnect

   Unplug the electrical connector for the NOx sensor.

4. 4

   Remove

   Carefully unscrew and remove the faulty NOx sensor from the exhaust pipe. (Penetrating oil may be required if the threads are seized from exhaust heat).

5. 5

   Install

   Thread the new NOx sensor into the exhaust pipe and tighten it to the manufacturer's specified torque.

6. 6

   Route the Harness

   Crucial step: Route the new NOx sensor harness exactly like the factory routing to avoid future heat soak and vibration failures.

7. 7

   Reconnect

   Plug in the electrical connector and reconnect the battery.

8. 8

   Clear Codes

   Use an AGCO diagnostic tool (EDT) to clear the fault code (003228.14 / SPN 3228 FMI 14) and run the engine to verify the sensor is reading correctly and the code does not return.