Case IH 19049 – Engine Control Unit (ECU) or Vehicle Control Module (VCM): Up and downstream NOx sensors swapped

This code indicates a plausibility error where the Engine Control Unit (ECU) or Vehicle Control Module (VCM) detects that the signals from the upstream (engine-out) and downstream (tailpipe) Nitrogen Oxide (NOx) sensors are reversed. Because the upstream and downstream NOx sensors on many Case IH machines share the exact same part number and connector type, they can easily be plugged into the wrong harness connectors during maintenance or exhaust repairs.

• Tier 4b
• Magnum (180-380)
• Puma (150-220)
• Maxxum (115-150)
• Farmall (110A-140A)
• Steiger/Quadtrac
• Axial-Flow 5140
• Axial-Flow 6140
• Axial-Flow 7140
• Axial-Flow 7240
• Axial-Flow 8240
• Axial-Flow 9240
• Patriot 2250
• Patriot 3240
• Patriot 3340
• Patriot 4440
• Titan 3040
• Titan 3540
• Titan 4040
• Titan 4540
• Case N-Series Loader Backhoes

1. 1

   Connect a diagnostic tool and monitor live data for both NOx sensors; upstream NOx ppm should be significantly higher than downstream.

2. 2

   Physically trace the wiring from the NOx sensors to the main engine harness to ensure the upstream harness is plugged into the upstream sensor module.

3. 3

   Check recent repair history to see if the exhaust system was removed, sensors replaced, or wiring harness disconnected recently.

1. 1

   Power Down

   Turn off the machine and wait for the aftertreatment system to complete its purge cycle and power down completely (listen for the DEF pump to stop clicking). Disconnect the battery to prevent electrical spikes.

2. 2

   Locate Connections

   Locate the control modules for both NOx sensors (the rectangular boxes attached to the sensor leads) and their connection points to the main equipment harness.

3. 3

   Swap Connectors

   Disconnect the upstream and downstream NOx sensors from the main harness and swap them to their correct respective plugs.

4. 4

   Physical Sensor Swap (If necessary)

   If the sensors were physically installed in the wrong exhaust bungs and the cord lengths are straining, use a 22mm wrench to remove them. Apply a high-temperature anti-seize compound to the threads (strictly avoiding the sensor tip) and reinstall them in the correct bungs. Torque to OEM specifications (typically around 50 Nm / 37 lb-ft).

5. 5

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use your diagnostic tool to clear fault code 19049.

6. 6

   Validation

   Start the engine and allow it to reach operating temperature so the SCR system begins dosing. Verify via the diagnostic tool that the upstream NOx reading is now higher than the downstream reading and that the code does not return.