Case IH 19566 – Engine Control Unit (ECU) / Vehicle Control Module (VCM): NOx Offset Min status based on the offset learned value

The engine's control system has detected that the learned offset value for the Nitrogen Oxide (NOx) sensor has drifted below the minimum acceptable threshold, indicating the sensor is reading out of range (implausible data) and can no longer accurately measure the NOx levels in the exhaust stream.

• Tier 4b
• Magnum 180
• Magnum 200
• Magnum 220
• Magnum 240
• Magnum 250
• Magnum 280
• Magnum 310
• Magnum 340
• Magnum 380
• Puma 150
• Puma 165
• Puma 185
• Puma 200
• Puma 220
• Maxxum 115
• Maxxum 125
• Maxxum 135
• Maxxum 145
• Maxxum 150
• Farmall 110A
• Farmall 120A
• Farmall 130A
• Farmall 140A
• Steiger
• Quadtrac
• Combine 5140
• Combine 6140
• Combine 7140
• Combine 7240
• Combine 8240
• Combine 9240
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Patriot 4440
• Titan 3040
• Titan 3540
• Titan 4040
• Titan 4540
• 580N
• 580SN
• 590SN

1. 1

   Inspect the wiring harness and the 5-pin connector leading to the NOx sensor for chafing, melting, corrosion, or loose pins.

2. 2

   Check for exhaust leaks upstream of the NOx sensor. An exhaust leak can introduce excess oxygen or alter exhaust flow, skewing the sensor's readings and causing a false offset error.

3. 3

   Using the Case Electronic Service Tool (EST), monitor the live NOx sensor output. A healthy NOx sensor typically reads around 500 ppm during the static warm-up phase. Once the exhaust temperature rises and DEF/AdBlue is injected, the reading should drop to approximately 250-270 ppm. If the sensor is stuck or reading erratically, it has failed.

4. 4

   Look for other SCR/DEF codes (e.g., 3521, 3528, 3529, 3530) which indicate open loads, short circuits, or plausibility failures directly tied to the sensor.

1. 1

   Power Down

   Turn off the machine, remove the key, and disconnect the negative battery cable to prevent electrical shorts.

2. 2

   Locate the Sensor

   Locate the faulty NOx sensor on the exhaust system. It is typically mounted downstream of the Diesel Oxidation Catalyst (DOC) and SCR catalyst.

3. 3

   Disconnect Wiring

   Unplug the sensor's electrical connector from the machine's wiring harness.

4. 4

   Remove the Sensor

   Using a specialized NOx sensor socket or a 22mm wrench, carefully unscrew the sensor from the exhaust pipe. Note: Exhaust sensors are prone to seizing. Apply penetrating oil to the threads and allow it to sit if the sensor is stuck.

5. 5

   Prepare the New Sensor

   Apply a small amount of high-temperature anti-seize compound to the threads of the new NOx sensor (if it does not come pre-applied from the factory). Do not get anti-seize on the sensor probe itself.

6. 6

   Install the New Sensor

   Thread the new sensor into the exhaust pipe by hand to prevent cross-threading, then tighten to the OEM torque specification.

7. 7

   Reconnect

   Plug the electrical connector back into the harness and secure any loose wiring with zip ties away from extreme heat sources.

8. 8

   Clear Codes and Reset

   Reconnect the battery. Connect the EST diagnostic tool, clear the 19566 fault code, and perform an SCR system test or run the machine through a complete warm-up cycle so the ECU can learn the new sensor's offset value.