Case IH 19549 – Engine Control Module (ECM) or Dosing Control Unit (DCU): Open circuit error for the NOx signal

The control module has lost communication with the Nitrogen Oxide (NOx) sensor due to a break in the electrical circuit, either within the wiring harness, the connector, or internally inside the sensor itself.

• Tier 4b
• Magnum (180, 200, 220, 240, 250, 280, 310, 340)
• Puma (150, 150 CVT, 165, 165 CVT)
• Farmall (110A, 120A, 130A, 140A)
• Combines (5140, 6140, 7140, 7240, 8240, 9240)
• Patriot (2250, 3240, 3340, 4440)
• Titan (3040, 3540, 4040, 4540)
• Case N-Series TLBs

1. 1

   Visual Inspection: Locate the NOx sensor (usually mounted on the exhaust pipe, either upstream or downstream of the SCR catalyst). Inspect the wiring harness leading to the sensor for chafing, cuts, or melted wires.

2. 2

   Connector Check: Disconnect the NOx sensor plug (commonly a 5-pin MCON plug). Check both sides of the connector for pushed-out pins, corrosion, or moisture intrusion.

3. 3

   Continuity Test: Using a multimeter, verify continuity on the signal, power, and ground wires between the NOx sensor harness connector and the ECM/DCU.

4. 4

   Voltage Check: Turn the key to the ON position and verify that the sensor is receiving the correct supply voltage (typically 12V or 24V depending on the machine's system) and has a solid ground.

5. 5

   If the wiring harness and voltages check out perfectly, the open circuit is internal to the NOx sensor, and the sensor must be replaced.

1. 1

   Turn off the machine, remove the key, and disconnect the battery

   This prevents electrical shorts.

2. 2

   Locate the faulty NOx sensor

   Find the sensor on the exhaust aftertreatment pipe.

3. 3

   Disconnect the electrical connector

   Disconnect it from the machine's wiring harness.

4. 4

   Unthread the NOx sensor from the exhaust bung

   Using an appropriate sensor socket or wrench, carefully unthread the NOx sensor. (Note: Penetrating oil may be required if the sensor is seized from exhaust heat).

5. 5

   Clean the threads of the exhaust bung

   Ensure no debris falls into the exhaust stream.

6. 6

   Apply anti-seize compound to the threads of the new NOx sensor

   Apply a small amount (if not already pre-applied by the manufacturer). Do not get anti-seize on the sensor probe itself.

7. 7

   Thread the new NOx sensor into the exhaust bung

   Tighten to the manufacturer's specified torque.

8. 8

   Route the sensor cable and plug in the connector

   Route the sensor cable safely away from extreme heat sources and moving parts, then plug the 5-pin connector back into the machine's harness.

9. 9

   Reconnect the battery

10. 10

    Clear the fault code and verify repair

    Connect a diagnostic tool to the machine, clear the 19549 fault code, and run the engine to verify the code does not return and the SCR system is functioning properly.