Massey Ferguson 5033.02 – Engine Control Unit (ECU) / EEM4: Issue With Exhaust Top NOx Sensor Module / Downstream NOx sensor value offset check error

The engine controller is receiving an inaccurate or offset reading from the downstream NOx sensor (located after the SCR catalytic converter), which monitors the nitrogen oxide levels in the exhaust gas to ensure the emissions system is functioning correctly. The Failure Mode Indicator (FMI) 2 indicates that the sensor data is erratic, implausible, or below the expected value.

• 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
• 5708
• 5709
• 5710
• 5711
• 5712
• 5713
• 6711
• 6712
• 6713
• 6714
• 6715
• 6716
• 6718
• 7340
• 7344
• 7345
• 7347
• 7360
• 7370
• 8727
• 8730
• 8732
• 8735
• 8737
• 8740

1. 1

   Inspect the downstream NOx sensor and its wiring harness for physical damage, wear, or melting

2. 2

   Check the 5-pin connector between the sensor and the ECU for loose, corroded, or contaminated pins

3. 3

   Ensure the sensor probe is not heavily contaminated with soot or oil, which can cause offset errors

4. 4

   Verify there are no exhaust leaks before the downstream sensor, as introduced oxygen can skew the NOx readings

5. 5

   Verify the sensor is receiving the correct supply voltage (12V or 24V depending on the system)

1. 1

   Turn off the machine and allow the exhaust system to cool completely.

2. 2

   Locate the downstream NOx sensor on the exhaust line, positioned after the SCR catalytic converter.

3. 3

   Disconnect the sensor's electrical connector from the wiring harness.

4. 4

   Carefully unscrew the sensor head from the exhaust pipe.

   Note: Do not use an impact wrench, as this can damage the threads.

5. 5

   Clean any carbon deposits from the exhaust pipe mounting hole before installing the new sensor.

6. 6

   Install the new genuine OEM NOx sensor.

   The sensor head thread is M20x1.5. Torque the sensor head to 50 Nm.

7. 7

   Route the sensor cable (typically 890mm long) safely away from extreme heat sources and reconnect the 5-pin plug.

8. 8

   Use a diagnostic service tool to clear the fault codes (SPN 5033 / 005033.02) and restart the engine to verify the repair.