Case IH 3528 – Engine Control Module (ECM) or Denoxtronic / SCR Control Unit (DCU): Downstream NOx sensor values are not plausible.

The engine's emissions control system is receiving data from the downstream Nitrogen Oxide (NOx) sensor that falls outside of the expected or physically possible range. This usually points to a failing sensor, a wiring/communication issue, or a severe anomaly in the exhaust stream (such as poor DEF/AdBlue quality or a failed SCR catalyst).

• Steiger T4B
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Magnum Series (180, 200, 220, 240, 250, 280, 310, 340, 380)
• Puma CVX Series (140, 145, 185, 200, 220)
• Farmall A Series (110A, 120A, 130A, 140A)

1. 1

   Check for Accompanying Codes: Look for related downstream NOx sensor codes (3529, 3530, 3531, or 3533).

2. 2

   Wiring and Connector Inspection: Inspect the downstream NOx sensor's 5-pin MCON connector and wiring harness for chafing, melting, or corrosion.

3. 3

   DEF/AdBlue Quality Check: Ensure the DEF fluid is not contaminated or diluted.

4. 4

   Exhaust Leak Check: Inspect the exhaust piping between the SCR catalyst and the downstream NOx sensor for leaks.

1. 1

   Preparation

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes. Allow the exhaust system to cool completely.

2. 2

   Locate the Sensor

   Locate the downstream NOx sensor, which is positioned in the exhaust pipe directly behind (downstream of) the SCR catalytic converter.

3. 3

   Disconnect

   Unplug the 5-pin electrical connector from the machine's wiring harness.

4. 4

   Removal

   Use a specialized NOx sensor socket or a wrench to remove the sensor from the exhaust pipe. If the sensor is seized, apply penetrating oil to the threads and allow it to sit before attempting removal.

5. 5

   Installation

   Thread the new NOx sensor into the exhaust pipe by hand to prevent cross-threading. Torque to OEM specifications. (Note: Most OEM sensors come with anti-seize pre-applied to the threads. Do not get anti-seize on the sensor probe itself).

6. 6

   Reconnect

   Plug the 5-pin connector back into the wiring harness, ensuring the locking tab clicks into place. Reconnect the battery.

7. 7

   Clear and Test

   Connect a diagnostic scan tool (such as the Case IH EST) to clear the stored 3528 / 319E fault code. Start the engine and perform a stationary regeneration or SCR system test to verify that the new sensor is reading plausible values and the code does not return.