New Holland 3528 – ECM: Nitrogen Oxide Sensor Integrity Error

The Engine Control Module (ECM) has detected an illogical or irrational signal from the Nitrogen Oxide (NOx) sensor, indicating an integrity error. The ECM continuously compares the readings from the inlet and outlet NOx sensors to monitor the efficiency of the Selective Catalytic Reduction (SCR) system. When the signal from a NOx sensor falls outside its expected range or does not correlate with other engine parameters, it is flagged as invalid. This affects the proper monitoring of nitrogen oxide levels in the exhaust system and suggests the sensor is failing or providing inaccurate data.

• T6 Series
• T6.125
• T7 Series
• T8 Series

1. 1

   Visually inspect the NOx sensor, wiring harness, and connectors for physical damage, corrosion, or moisture ingress

2. 2

   Examine the sensor head for contamination (a black, sooty deposit indicates oil consumption; white crystal formations indicate excessive DEF injection)

3. 3

   Verify the ECM has a stable power supply and a clean, tight ground connection to rule out voltage drops

4. 4

   Inspect the exhaust system for any leaks upstream of the NOx sensor that could alter sensor readings

5. 5

   Review other active or stored fault codes (faults related to the SCR system, DEF injector, or other emission components can trigger a NOx sensor plausibility code)

1. 1

   Disconnect batteries

   Disconnect the vehicle's batteries to prevent electrical shock before beginning the repair.

2. 2

   Locate the sensor

   The NOx sensor assembly consists of a sensor probe screwed into the exhaust pipe and an electronic module connected via a harness. There are typically two NOx sensors: an inlet (pre-SCR) and an outlet (post-SCR) sensor. Identify the faulty sensor based on the specific diagnostic trouble code.

3. 3

   Remove the module

   Disconnect the electrical connector from the NOx sensor module. Unbolt the module from its mounting bracket.

4. 4

   Remove the sensor probe

   Apply penetrating oil to the sensor threads if it is seized in the exhaust pipe. Use a specialized NOx sensor socket or an oxygen sensor socket to loosen and remove the sensor probe from the exhaust. If the sensor is heavily seized and will be replaced, it may be necessary to cut the wire and use a standard deep-well socket for removal.

5. 5

   Install the new sensor

   Clean the threads in the exhaust port using a thread chaser (e.g., M20 x 1.5) to ensure a smooth installation. Thread the new sensor in by hand to avoid cross-threading. Torque the new sensor to the manufacturer's specification (typically 48-55 Nm). Do not use anti-seize compound unless specified by the part manufacturer, as many new sensors have a pre-applied coating.

6. 6

   Install the new module

   Mount the new NOx sensor module securely to its bracket and reconnect the electrical connector, ensuring it clicks into place.

7. 7

   Reconnect and relearn

   Reconnect the batteries. Use a diagnostic scan tool to clear the fault code from the ECM. Perform a NOx sensor relearn or calibration procedure as required by the manufacturer. This step is crucial for the system to recognize the new sensor and function correctly. A test drive may be necessary to complete the relearn process and verify the repair.