Massey Ferguson 5028.31 – Engine Control Unit (ECU): Issue With DOC NOx Sensor Module. (ECU)

Malfunction, communication failure, or out-of-range reading from the Nitrogen Oxide (NOx) sensor module located at the Diesel Oxidation Catalyst (DOC) / exhaust inlet. The NOx sensor monitors the exhaust gas composition to help the system manage AdBlue/DEF dosing and emissions compliance.

• 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
• MF 4707
• MF 5608
• 5609
• 5610
• 5611
• 5612
• 5613
• MF 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• MF 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• MF 7714

1. 1

   Check the Power Supply: Verify battery voltage during crank and check the charging system, as power supply issues under load can cause sensor faults.

2. 2

   Inspect the Wiring Harness: Check the wiring harness leading to the DOC NOx sensor for rub points, melted insulation from exhaust heat, or pinched wires.

3. 3

   Check the Connector: Disconnect the NOx module electrical connector and inspect the pins for corrosion, moisture, or pushed-out terminals.

4. 4

   Verify Ground Integrity: Ensure the ECU and exhaust system grounds are clean and tight.

1. 1

   Turn off the engine and allow the exhaust system (specifically the DOC and SCR modules) to cool completely to avoid severe burns.

   Allow exhaust system to cool completely.

2. 2

   Locate the DOC NOx sensor (this is the sensor located before the DOC / at the exhaust inlet).

   Locate the DOC NOx sensor.

3. 3

   Detach the NOx sensor wiring harness from its retaining clips along the frame/exhaust shield.

   Detach wiring harness from retaining clips.

4. 4

   Disconnect the in-line electrical connector for the NOx module.

   Disconnect the in-line electrical connector.

5. 5

   Using a specialized NOx sensor socket or a wrench, carefully unscrew the sensor probe from the exhaust pipe bung. (If seized, penetrating oil may be required).

   Unscrew the sensor probe from the exhaust pipe bung.

6. 6

   Apply a small amount of anti-seize compound to the threads of the new sensor (if not already pre-applied by the manufacturer), being extremely careful not to get any on the sensor tip.

   Apply anti-seize compound to the threads of the new sensor.

7. 7

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

   Thread and tighten the new NOx sensor.

8. 8

   Route the new wiring harness exactly as the old one was routed, securing it into the clips to keep it away from direct exhaust heat.

   Route and secure the new wiring harness.

9. 9

   Reconnect the electrical connector.

   Reconnect the electrical connector.

10. 10

    Connect a diagnostic tool (such as Jaltest or the AGCO diagnostic tool) to clear the fault codes and perform any necessary aftertreatment resets.

    Clear fault codes and perform aftertreatment resets.