Massey Ferguson 3234.03 – ECU: NOx Sensor Outlet SCR Signal Issue. (ECU)

The engine control system is detecting an abnormal electrical signal from the Nitrogen Oxide (NOx) sensor located downstream (at the outlet) of the Selective Catalytic Reduction (SCR) catalyst. An FMI of .03 indicates that the sensor's voltage is above normal or shorted to a high source, preventing accurate measurement of emissions.

• 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

   Inspect the wiring harness running from the ECU to the outlet NOx sensor module for melted wires, chafing against the chassis, or rodent damage

2. 2

   Disconnect the NOx sensor plug and check for water ingress, DEF fluid contamination, or bent/corroded pins

3. 3

   Using a multimeter, verify that the sensor is receiving proper supply voltage and has a solid ground

4. 4

   Verify the CAN High and CAN Low lines at the sensor connector for proper voltage and continuity

5. 5

   Ensure there are no exhaust leaks near the sensor bung, which can skew readings and cause implausible signal faults

1. 1

   Power Down

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

2. 2

   Locate the Sensor

   Locate the Outlet NOx sensor on the exhaust pipe. It will be positioned downstream of the SCR catalyst/DPF assembly.

3. 3

   Disconnect

   Unplug the electrical connector linking the sensor module to the main harness.

4. 4

   Remove the Sensor

   Using a specialized NOx sensor socket or a wrench, unscrew the sensor probe from the exhaust bung. (Note: Exhaust sensors are prone to seizing. Apply penetrating oil and allow it to soak if the sensor is stuck).

5. 5

   Install the New Sensor

   Apply a small amount of high-temperature anti-seize to the threads of the new sensor (if not pre-applied by the manufacturer). Thread it into the exhaust bung and tighten to the OEM torque specification.

6. 6

   Route Wiring

   Securely mount the new sensor's control module and route the wiring harness away from extreme heat sources. Reconnect the electrical plug.

7. 7

   Clear Codes

   Reconnect the battery. Connect the AGCO Electronic Diagnostic Tool (EDT) to clear the fault codes. You may need to run a stationary SCR system test or reset the NOx sensor adaptations so the ECU recognizes the new component.