Case IH 3528 (F-519045-02) – Engine ECU (Engine Control Module): Downstream NOx sensor values are not plausible

The Engine Control Unit is receiving readings from the downstream (post-SCR) Nitrogen Oxide (NOx) sensor that do not align with the expected values based on current engine load, exhaust temperatures, and DEF (AdBlue) dosing rates. This typically triggers an 'SCR Failure' warning and can lead to engine torque limitation (derate) if not addressed.

• VESTRUM CVX
• Magnum (180, 190, 200, 210, 220, 225, 235, 240, 250, 260, 280, 290, 310, 315, 340, 370, 380)
• Steiger (350 to 600)
• Quadtrac (370 to 620)
• Farmall (110A to 140A)
• Maxxum (115 to 150)
• Puma (150 to 220)
• 240 Series
• 5130
• 6130
• 7130
• 7230
• 8230
• 9230
• 2240
• 4430
• Titan 3030
• Titan 3530
• Titan 4030
• Titan 4530
• 521F
• 621F
• 821F
• 921F
• 1021F
• 1121F

1. 1

   Check for companion codes (e.g., 3529, 3530, or 3533). If present, diagnose wiring harness or connector issues first.

2. 2

   Inspect the downstream NOx sensor harness for open circuits, shorts to ground, or poor electrical connections at the pins.

3. 3

   Verify that the DEF fluid is not contaminated and that the DEF dosing valve is functioning properly.

4. 4

   Check for an exhaust leak upstream of the sensor, which can skew NOx readings.

1. 1

   Turn off machine and disconnect battery

   Turn off the machine and disconnect the battery to prevent electrical spikes. Ensure the exhaust system has completely cooled, as NOx sensors operate at extremely high temperatures.

2. 2

   Locate downstream NOx sensor

   Locate the downstream NOx sensor. It is mounted in the exhaust pipe after the SCR catalyst/muffler.

3. 3

   Disconnect electrical connector

   Disconnect the electrical connector linking the NOx sensor control module (ballast) to the machine's wiring harness.

4. 4

   Unbolt sensor module

   Unbolt the sensor module from its mounting bracket.

5. 5

   Unscrew sensor probe

   Using a specialized NOx/O2 sensor socket or wrench, carefully unscrew the sensor probe from the exhaust pipe boss. (Penetrating oil may be required if the threads are seized).

6. 6

   Install new NOx sensor probe

   Install the new NOx sensor probe into the exhaust boss and tighten to the OEM torque specification.

7. 7

   Mount new sensor control module

   Mount the new sensor control module and reconnect the electrical harness.

8. 8

   Reconnect battery

   Reconnect the battery.

9. 9

   Clear codes

   Connect a diagnostic tool to clear the 3528 fault code. The system may require a run cycle or a forced stationary regeneration to validate the repair and clear the SCR derate state.