Massey Ferguson E521005.12 – Engine ECU: NOx Sensor Before DOC Signal Issue

NOx sensor before DOC - Time required to stabilise the sensor has elapsed. The engine control system is monitoring the upstream NOx sensor (located before the Diesel Oxidation Catalyst), but the sensor is failing to provide a stable, readable signal within the programmed time limit after startup.

• 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
• 6600
• 6700
• 7700
• 8600
• 8700

1. 1

   Inspect the wiring harness leading to the upstream NOx sensor (before the DOC) for melted wires, chafing, or corrosion inside the connector plug.

2. 2

   Verify that the sensor is receiving proper voltage and ground, and that the CAN High/CAN Low lines have continuity to the ECU.

3. 3

   Inspect the exhaust piping between the engine manifold and the DOC for exhaust leaks, which can introduce excess oxygen or disrupt exhaust flow.

4. 4

   Check if there is an ECU software update available from AGCO to widen the acceptable time parameters for NOx sensor stabilization.

1. 1

   Preparation

   Turn off the tractor, remove the key, and disconnect the negative battery cable. Allow the exhaust system to cool completely.

2. 2

   Locate the Sensor

   Locate the upstream NOx sensor. It is threaded into the exhaust pipe before the DOC (Diesel Oxidation Catalyst) housing.

3. 3

   Disconnect

   Unplug the sensor's electrical connector from the main engine harness.

4. 4

   Removal

   Use a specialized NOx sensor socket (or a 22mm wrench) to remove the sensor. Tip: Exhaust sensors are prone to seizing. Apply penetrating oil to the threads and allow it to sit if the sensor is stuck.

5. 5

   Preparation of New Sensor

   Check the threads of the new OEM sensor. If it does not have anti-seize compound pre-applied, apply a small amount of high-temperature exhaust anti-seize to the threads. Do not get any compound on the sensor probe tip, as this will ruin it.

6. 6

   Installation

   Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten to the manufacturer's specified torque.

7. 7

   Reconnection

   Route the wiring safely away from extreme heat sources and plug the connector back into the harness.

8. 8

   Clear Codes

   Reconnect the battery. Connect a diagnostic tool (such as AGCO EDT) to clear the E521005.12 fault code. Run the engine up to operating temperature to ensure the new sensor stabilizes and the code does not return.