Case IH 19565 – Engine Control Module (ECM) or Vehicle Control Module (VCM) / Denoxtronic Control Unit (DCU): NOx Offset Max status based on the offset learned value

This code indicates that the Engine Control Module (ECM) has reached the maximum allowable offset adjustment for the Nitrogen Oxide (NOx) sensor reading. The system continuously learns and adjusts the NOx sensor's baseline (offset) to compensate for normal sensor aging and drift. When the required adjustment hits the maximum programmed limit, it triggers this code. This typically means the NOx sensor is failing, drifting excessively, or there is an underlying emissions issue (such as a degraded SCR catalyst or exhaust leak) causing the sensor to max out its adaptation.

• Tier 4b
• Magnum (180, 200, 220, 240, 250, 280, 310, 340, 370)
• Steiger / Quadtrac (350, 400, 450, 500, 550, 600)
• Puma (150, 165)
• Axial-Flow 5130
• Axial-Flow 6130
• Axial-Flow 7130
• Axial-Flow 7230
• Axial-Flow 8230
• Axial-Flow 9230
• Axial-Flow 5140
• Axial-Flow 6140
• Axial-Flow 7140
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9240
• Patriot (2250, 3240, 3340, 4440)
• Titan (3030, 3530, 4030, 4530)
• Case N-Series TLBs
• F-Series Wheel Loaders (521F, 621F, 821F, 921F)

1. 1

   Verify the Diesel Exhaust Fluid (DEF) concentration is at the required ~32.5% urea using a refractometer.

2. 2

   Inspect the exhaust system for leaks upstream of the SCR catalyst and the NOx sensor.

3. 3

   Inspect the NOx sensor wiring harness and the 5-pin MCON connector for physical damage, melted wires, or corrosion.

4. 4

   Check for accompanying codes related to the SCR dosing valve, EGR system, or DEF pressure and diagnose them first.

5. 5

   Use the CNH Electronic Service Tool (EST) to perform a NOx sensor plausibility test to observe the sensor's live response.

1. 1

   Disconnect power

   Turn off the machine and disconnect the master battery switch to prevent electrical spikes.

2. 2

   Locate the NOx sensor

   Locate the affected NOx sensor on the exhaust aftertreatment pipe (verify via your diagnostic tool if it is the upstream or downstream sensor).

3. 3

   Disconnect electrical connector

   Disconnect the sensor's electrical connector from the main harness.

4. 4

   Remove the NOx sensor

   Carefully unscrew the NOx sensor probe from the exhaust pipe. Use penetrating oil if the threads are seized to avoid damaging the exhaust bung.

5. 5

   Install the new NOx sensor

   Apply a small amount of anti-seize compound to the threads of the new sensor (if not pre-applied from the factory) and install it into the exhaust pipe. Torque to OEM specifications.

6. 6

   Reconnect the sensor

   Route the sensor module and cable away from extreme heat sources and reconnect the electrical plug.

7. 7

   Reset learned values

   Connect the CNH EST diagnostic tool. You must clear the fault codes and reset the NOx sensor learned values/adaptations in the ECM. If you do not reset the learned offset, the ECM will apply the old, maxed-out offset to the new sensor, and the code will return.

8. 8

   Verify the repair

   Run the engine and perform a forced SCR system test or a test drive to verify the repair.