Case IH 19422 – Engine Control Module (ECM) or Urea Control Module (UCM) / SCR Controller: Downstream NOx sensor signal is stuck at a constant value.

The engine or emissions controller is receiving a static, unchanging signal from the downstream Nitrogen Oxide (NOx) sensor. A constant value indicates that the sensor's internal logic has frozen, the sensor probe is fouled/damaged, or there is a wiring issue preventing data transmission.

• Tier 4b
• 240 Series Axial-Flow Combines (7240, 8240, 9240)
• Farmall (110A, 115U, 120A, 130A, 140A)
• Magnum (180 through 380)
• Maxxum (115 through 150)
• Puma (150 through 220)
• Steiger 4WD Tractors (370 through 500)
• Case Construction N Series Loaders

1. 1

   Check for accompanying codes: If DTC 43CE (19422) is present alongside DTC 38CB (NH3 sensor signal not changing) or DTC 2DDA (SCR catalyst efficiency lower than threshold), resolve the electrical/sensor fault first before diagnosing the catalyst.

2. 2

   Visual wiring inspection: Inspect the downstream NOx sensor harness and connectors for physical damage, bent or dislocated pins, corroded terminals, or broken wires.

3. 3

   Connector seating: Verify that the sensor's electrical connector is fully seated and locked.

4. 4

   Flex test: While monitoring the sensor data on the Case IH Electronic Service Tool (EST) or machine display, gently flex the involved wiring harnesses to reveal any intermittent breaks or shorts in the wiring.

5. 5

   Circuit testing: Use a multimeter to check for continuity, as well as shorts to ground or shorts to battery voltage within the NOx sensor circuit.

1. 1

   Power Down

   Turn off the engine and engage the battery disconnect switch. Allow the exhaust system to cool completely, as the SCR system operates at extremely high temperatures.

2. 2

   Locate the Sensor

   Locate the downstream NOx sensor, which is threaded into the exhaust pipe after the SCR catalytic converter.

3. 3

   Disconnect Electronics

   Unplug the electrical connector linking the NOx sensor to the machine's wiring harness.

4. 4

   Remove the Sensor

   Carefully unscrew the NOx sensor from the exhaust bung. (Note: Use penetrating oil if the sensor is seized. Thread damage to the exhaust bung can complicate the repair and void replacement eligibility).

5. 5

   Install the New Sensor

   Thread the new downstream NOx sensor into the exhaust bung and tighten it to the OEM specified torque.

6. 6

   Route Wiring

   Reconnect the electrical connector. Ensure the sensor's wiring pigtail is routed safely away from extreme heat sources and moving parts.

7. 7

   Clear Codes

   Reconnect the battery power. Connect the Case IH Electronic Service Tool (EST) to clear the recorded 19422 fault code from the ECM/UCM.

8. 8

   Verify Repair

   Start the engine and allow it to reach operating temperature. Monitor the downstream NOx sensor signal via the EST to verify the signal is now fluctuating normally and the fault code does not return.