Massey Ferguson 3222.03 – Engine Control Unit (ECU): NOx Sensor Before DOC Signal Issue. (ECU)

This code indicates that the Engine Control Unit (ECU) is receiving an abnormal signal from the upstream Nitrogen Oxide (NOx) sensor, which is located in the exhaust stream before the Diesel Oxidation Catalyst (DOC). In standard J1939 fault code architecture, an FMI of .03 typically translates to "Voltage Above Normal, or Shorted to High Source." This means the ECU is detecting a circuit that is either shorted to power or completely open, rather than a purely emissions-related reading error.

• 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
• 7714S
• 7719S

1. 1

   Inspect the wiring harness leading to the upstream NOx sensor (before the DOC) for chafing, melting from exhaust heat, or rodent damage.

2. 2

   Disconnect the NOx sensor module plug. Check for water intrusion, bent pins, or corrosion.

3. 3

   Using a multimeter, verify that the sensor is receiving proper supply voltage and has a solid ground. Test the signal wire for continuity back to the ECU harness and ensure it is not shorted to a 12V/24V power source.

4. 4

   Ensure there are no exhaust leaks between the engine manifold and the DOC that could damage the sensor wiring via escaping heat.

1. 1

   Power Down

   Turn off the tractor and disconnect the negative battery terminal to prevent electrical spikes.

2. 2

   Locate the Sensor

   Locate the upstream NOx sensor threaded into the exhaust pipe just before the DOC canister. Follow its wire to the mounted NOx control module box.

3. 3

   Disconnect

   Unplug the electrical connector from the NOx sensor module. Unbolt the module from its mounting bracket.

4. 4

   Remove the Sensor

   Using a specialized NOx/O2 sensor socket or a flare-nut wrench, carefully unscrew the sensor probe from the exhaust pipe. (Note: Exhaust sensors are prone to seizing. Apply penetrating oil to the threads and allow it to soak if resistance is high).

5. 5

   Install the New Sensor

   Apply a small amount of anti-seize compound only to the threads of the new sensor (avoiding the sensor tip). Thread it into the exhaust pipe and tighten to the OEM torque specification.

6. 6

   Mount and Reconnect

   Secure the new NOx control module to the mounting bracket and plug in the electrical connector.

7. 7

   Clear Codes

   Reconnect the battery. Use an AGCO/Massey Ferguson compatible diagnostic scan tool to clear the 003222.03 fault code.

8. 8

   Test Run

   Start the engine and allow it to reach operating temperature to verify the code does not return.