Massey Ferguson 3222.05 – Engine ECU: NOx Sensor Before DOC Signal Issue

The FMI 05 designation means 'Current Below Normal or Open Circuit.' This indicates that the controller has detected a break in the circuit, a disconnected plug, or an internal failure within the NOx sensor module itself, resulting in a loss of the expected electrical signal from the upstream NOx sensor (located before the Diesel Oxidation Catalyst / DOC).

• 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
• 7714S
• 7719S

1. 1

   Visually inspect the wiring harness between the NOx sensor control module and the main engine harness for chafing, melting, or cuts.

2. 2

   Disconnect the NOx sensor plug and check for pushed-out pins, corrosion, or water ingress.

3. 3

   With the key ON, use a multimeter to verify that the NOx sensor is receiving proper supply voltage (12V or 24V) and has a solid ground.

4. 4

   With the batteries disconnected, measure the resistance across the CAN High and CAN Low pins at the sensor connector (should read approximately 60 ohms, indicating intact terminating resistors).

5. 5

   If power, ground, and CAN lines are intact, use a scan tool to verify the open circuit is internal to the NOx sensor module, which will require replacement.

1. 1

   Power Down

   Turn off the machine and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Locate the Sensor

   Identify the NOx sensor located before the DOC in the exhaust stream. Note that the sensor consists of a probe in the exhaust pipe, a connecting cable, and a small control module box. These cannot be separated and must be replaced as a single unit.

3. 3

   Disconnect

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

4. 4

   Remove the Probe

   Carefully unscrew the NOx sensor probe from the exhaust bung. Tip: Apply penetrating oil to the threads and allow it to soak if the sensor is seized, to avoid stripping the exhaust pipe threads.

5. 5

   Install New Sensor

   Apply a small amount of anti-seize to the threads of the new sensor (avoid getting any on the sensor tip). Thread it into the exhaust bung and tighten to the manufacturer's torque specification.

6. 6

   Mount and Route

   Secure the new NOx sensor control module to the mounting bracket. Route the cable safely away from extreme heat sources and moving parts. Reconnect the electrical harness.

7. 7

   Clear Codes

   Reconnect the battery. Use a diagnostic scan tool to clear the 003222.05 fault code.

8. 8

   Test Drive

   Run the engine. Note that NOx sensors do not begin broadcasting data immediately; the exhaust must reach a specific 'dew point' temperature (often around 120°C) to ensure no moisture is present before the sensor activates. Run the tractor under load to verify the code does not return.