Massey Ferguson 3224.03 – Engine ECU: NOx Sensor Before DOC Signal Issue. (ECU)

The code indicates a signal issue with the Nitrogen Oxide (NOx) sensor located upstream of the Diesel Oxidation Catalyst (DOC). The ".03" suffix (FMI 03) indicates "Voltage Above Normal, or Shorted to High Source," meaning the controller is seeing a higher voltage return than expected, usually pointing to a short circuit, a broken ground, or an internally failed sensor.

• 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
• 7714 to 7726
• 8727 to 8740

1. 1

   Inspect the wiring harness leading to the NOx sensor before the DOC for chafed wires, melted insulation from exhaust heat, or physical damage

2. 2

   Disconnect the NOx sensor control module connector and check for water intrusion, bent pins, or corrosion

3. 3

   Verify that the sensor is receiving proper supply voltage (12V or 24V) and has a solid ground (a missing ground can cause a Voltage Above Normal FMI 03 fault)

4. 4

   Verify CAN High and CAN Low resistance and voltage on the auxiliary engine CAN bus

5. 5

   Ensure there are no exhaust leaks upstream of the DOC, as unmetered air can skew sensor readings

1. 1

   Power Down

   Turn the tractor's main battery disconnect switch to the OFF position before handling electrical or emissions components.

2. 2

   Locate the Sensor

   Locate the upstream NOx sensor. It consists of two parts permanently joined by a cable: a sensor head threaded into the exhaust pipe (before the DOC) and a small control unit bolted to the chassis/bracket.

3. 3

   Disconnect

   Unplug the electrical connector from the NOx sensor control unit.

4. 4

   Remove Sensor Head

   Unbolt the control unit. Then, using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor head from the exhaust pipe. (Note: The sensor head thread is M20x1.5. Penetrating oil may be required if it is seized).

5. 5

   Install New Sensor

   Thread the new sensor head into the exhaust pipe. Torque the sensor head to exactly 50 Nm (37 lb-ft).

6. 6

   Mount Control Unit

   Secure the new sensor's control unit to its mounting bracket.

7. 7

   Reconnect & Clear

   Reconnect the electrical harness. Turn the battery switch back on, connect a diagnostic tool (like AGCO EDT), clear the inactive 003224.03 fault code, and run the engine to verify the repair.