Massey Ferguson E521004.02 – Engine Control Unit (ECU): NOx Sensor Top Of Exhaust Signal Issue

Indicates a malfunction, implausible reading, or communication failure with the upstream Nitrogen Oxide (NOx) sensor, which is located at the top of the exhaust system before the Selective Catalytic Reduction (SCR) catalyst.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 4707
• 4708
• 4709
• 4710
• 5710 SL
• 5711 SL
• 5712 SL
• 5713 SL
• 7714
• 7715
• 7716
• 7718
• 7719
• 7720
• 7722
• 7724
• 7726

1. 1

   Inspect the wiring harness leading to the upstream NOx sensor for heat soak damage, melted wires, or vibration wear

2. 2

   Disconnect the sensor and check the connector pins for corrosion, moisture, or loose connections

3. 3

   Perform an exhaust leak test on the manifold and piping prior to the sensor, as outside oxygen can skew NOx readings

4. 4

   Remove the sensor and visually inspect the ceramic probe for heavy soot or oil contamination

1. 1

   Preparation

   Turn off the tractor, disconnect the battery, and allow the exhaust system to cool completely.

2. 2

   Removal

   Locate the upstream NOx sensor at the top of the exhaust pipe (before the DPF/SCR unit). Disconnect the electrical connector from the wiring harness.

3. 3

   Unthread the Sensor

   Use a specialized NOx/O2 sensor socket to carefully unthread the sensor. Note: Do not use an impact wrench, as this can damage the exhaust bung threads.

4. 4

   Clean the Port

   Clean any carbon deposits from the exhaust pipe threads before installing the new part.

5. 5

   Installation

   Carefully thread the new NOx sensor into the exhaust by hand to prevent cross-threading. Crucial: Do not touch the ceramic probe with your bare fingers, as oil contamination will cause immediate failure. Torque to the manufacturer's specification.

6. 6

   Routing

   Reconnect the electrical harness. Route the wiring exactly as it was from the factory to prevent future heat soak or vibration failures.

7. 7

   Clear Codes

   Reconnect the battery and use a diagnostic tool to clear the E521004.02 fault code from the ECU.