Massey Ferguson E521005.02 – Engine Control Unit (ECU) / EEM4: NOx Sensor Before DOC Signal Issue / Upstream NOx sensor value implausible

The EEM4 (Electronic Engine Management 4) monitoring system has detected an implausible reading from the upstream NOx sensor (the sensor located before the Diesel Oxidation Catalyst / DOC). The sensor value is evaluated during the driving cycle, and this code triggers when the plausibility test results in a failure.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• MF 4707
• MF 4708
• MF 4709
• MF 4710
• MF 5608
• MF 5609
• MF 5610
• MF 5611
• MF 5612
• MF 5613
• MF 5710 SL
• MF 5711 SL
• MF 5712 SL
• MF 5713 SL
• MF 7614
• MF 7615
• MF 7616
• MF 7618
• MF 7619
• MF 7620
• MF 7622
• MF 7624
• MF 7626
• MF 7714 through 7726S

1. 1

   Verify that the upstream NOx sensor is installed correctly in the exhaust pipe before the DOC

2. 2

   Check the voltage converter operation if there is one present in the system

3. 3

   Check the operation by temporarily swapping the sensor with another known-good NOx sensor to confirm if the original sensor is defective

4. 4

   Ensure there are no open wires or short circuits in the NOx sensor harness

1. 1

   Turn off the tractor and disconnect the battery

   Ensure safety while working on the exhaust system.

2. 2

   Locate the upstream NOx sensor

   Positioned in the exhaust stream before the Diesel Oxidation Catalyst / DOC.

3. 3

   Disconnect the electrical harness connector

   Disconnect the connector for the NOx sensor.

4. 4

   Unscrew the defective NOx sensor from the exhaust pipe

   Carefully unscrew it. Penetrating oil may be required if the threads are seized from exhaust heat.

5. 5

   Install the new OEM upstream NOx sensor

   Ensure it is seated and torqued correctly to prevent exhaust leaks, which can skew sensor readings.

6. 6

   Reconnect the electrical harness

   Reconnect the harness to the new NOx sensor.

7. 7

   Clear the fault code

   Reconnect the battery, turn on the machine, and use a diagnostic service tool to clear the E521005.02 / SPN 521005 fault code.

8. 8

   Run the tractor through a standard driving cycle

   Ensure the EEM4 system successfully passes the NOx plausibility test and the code does not return.